storage interview question

This is a big collection of questions asked in interviews in different Domains.

storage interview question

Unread postby rajeevmahura » Tue Aug 19, 2008 10:56 am

We had 10 SAN interview questions in our earlier blogpost - Answers are given below

1) What is the differerence b/w SAN and NAS ?

The basic difference between SAN and NAS , SAN is Fabric based and NAS is Ethernet based.
SAN - Storage Area Network
NAS - Network attached Storage

2)What is a typical storage area network consists of - if we consider it for implementation in a small business setup ?
If we consider any small buisenss following are essentials componets of SAN

- Fabric Switch
- FC Controllers
- JBOD's

3)Can you briefly explain each of these Storage area components?
Fabric Swictch: It's a device which interconnects multiple network devices .There are swithes starting from 16 port to 32 ports which connect 16 or 32 machine nodes etc.Vendors who manufacture these kind of switches are Brocade, McData.

FC Controllers : These are Data transfer medias they will sit on PCI slots of Server,u can configure Arrays and volumes on it.

JBOD: Just Bunch of Disks is Storage Box,it consists of Enclosure where set of harddrives are hosted in many combinations such SCSI drives,SAS ,FC,SATA.

4)What is the most critical component in SAN ?
Each component has its own criticality with respect to buisness needs of a company.

5) Define RAID ? Which one you feel is good choice ?

RAID (Redundant array of Independent Disks) is a technology to achive redundancy with faster I/O.There are Many Levels of RAID to meet different needs of the customer which are : R0,R1,R5,R10,R5.
Generally customer choose R5 to achive better redundancy and speed and it is cost effective.

6)How is a SAN managed ?

There are many management softwares used for managing SAN's to name a few

- Santricity
- IBM Tivoli Storage Manager.
- CA Unicenter.
- Veritas Volumemanger.

7) Which one is the Default ID for SCSI HBA ?

Generally the default ID for SCSI HBA is 7.
SCSI- Small Computer System Interface
HBA - Host Bus Adaptor

8) How do you install device drivers for the HBA first time during OS installation ?

In some scenarios you are supposed to install Operating System on the drives connected thru SCSI HBA or SCSI RAID Conrollers,but most of the OS'es will not be updated with drivers for those controllers,that time you need to supply drivers externally,if you are installing windows ,you need to press F6 during the installion of OS and provide the driver disk or CD which came along with HBA.
If you are installing linux you need to type "linux dd" for installing any driver.

9) What is Array ?

Array is a group of Independent physical disks to configure any Volumes or RAID volumes.

10)Can u describe atleast 3 troubleshooting scenarios which you have come across in detail ?

SCENARIO 1:How do you find/debug when there is error while working SCSI devices?

In our daily SAN troubleshooting there are many management and configuration tools we use them to see when there is a failure with target device or initiator device.
Some time it is even hard to trouble shoot some of the things such as media errors in the drives, or some of the drives taking long time to spinnup.In such cases these utilities will not come to help.To debug this kind of information most of the controller will be implemented with 3-pin serial debug port. With serial port debug connector cable you can collect the debug information with hyper terminal software.


SCENARIO 2: I am having an issue with a controller its taking lot of time to boot and detect all the drives connected how can I solve this.?

There are many possibilities that might cause this problem. One of the reason might be you are using bad drives that cannot be repaired . In those cases you replace the disks with working ones.

Another reason might be slots you connected your controller to a slot which might not be supported.
Try to connect with other types of slots.

One more probable reason is if you have flashed the firmware for different OEM’s on the same hardware.
To get rid of this the flash utilities will be having option to erase all the previous and EEPROM and boot block entry option. Use that option to rectify the problem.

SCENARIO 3: I am using tape drive series 700X , even the vendor information on the Tape drive says 700X, but the POST information while booting the server is showing as 500X what could be the problem?

First you should make sure your hardware is of which series , you can find out this in the product website.
Generally you can see this because in most of the testing companies they use same hardware to test different series of same hardware type. What they do is they flash the different series firmware. You can always flash back to exact hardware type.

Below are the 10 questions asked in an interview with SAN company StorageTek .
1) Which are the SAN topologies?

Answer :SAN can be connected in 3 types which are mentioned below:
Point to Point topology
FC Arbitrated Loop ( FC :Fibre Channel )
Switched Fabric

2) Which are the 4 types of SAN architecture types
Answer :Core-edge
Full-Mesh
Partial-Mesh
Cascade

3) which command is used in linux to know the driver version of any hardware device ?
Answer : dmesg

4) How many minimum drives are required to create R5 ( RAID 5) ?

Answer : You need to have at least 3 disk drives to create R5.

5) Can you name some of the states of RAID array ?

Answer : There are states of RAID arrays that represent the status of the RAID arrays which are given below
online
Degraded
Rebuilding
Failed

6) Name the features of SCSI-3 standard ?

Answer : QAS: Quick arbitration and selection
Domain Validation
CRC: Cyclic redundancy check

7) Can we assign a hot spare to R0 (RAID 0)array?

Answer :No, since R0 is not redundant array, failure of any disks results in failure of the entire array so we cannot rebuild the hot spare for the R0 array.

8) Can you name some of the available tape media types ?

Answer :There are many types of tape media available to back up the data some of them are
DLT :digital linear tape - technology for tape backup/archive of networks and servers; DLT technology addresses midrange to high-end tape backup requirements.
LTO :linear tape open; a new standard tape format developed by HP, IBM, and Seagate.
AIT :advanced intelligent tape; a helical scan technology developed by Sony for tape backup/archive of networks and servers, specifically addressing midrange to high-end backup requirements.

9) what is HA ?

Answer : HA High Availability is a technology to achive failover with very less latency. Its a practical requirement of data centers these days when customers expect the servers to be running 24 hours on all 7 days around the whole 365 days a year - usually referred as 24x7x365. So to achieve this a redundant infrastructure is created to make sure if one database server or if one app server fails there is a replica Database or Appserver ready to takeover the operations. End customer never experiences any outage when there is a HA network infrastructure.

10) What is virtualization?

Answer :Virtualization is logical representation of physical devices. It is the technique of managing and presenting storage devices and resources functionally, regardless of their physical layout or location.Virtualization is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console. Storage virtualization is commonly used in a storage area network (SAN). The management of storage devices can be tedious and time-consuming. Storage virtualization helps the storage administrator perform the tasks of backup, archiving, and recovery more easily, and in less time, by disguising the actual complexity of the SAN.
Virtualization is a topic of real importance and will be covered in detail in one of our future blogpost.




1. What is RAID?
2. What are the advantages of RAID?
3. What are different levels of RAID?
4. Explain RAID0, RAID1, RAID5 ?
5. Whats the difference between RAID0 & RAID1 ?
6. Whats the difference between RAID1 & RAID5 ?
7. Whats the difference between RAID3 & RAID5 ?
8. Whats the difference between RAID01 & RAID10 ?
9. How many minimum disk drives are needed for R0,R1,R5,R10,R01 ?
10.How RAID 5 works and how parity is calculated ?
11.Other than RAID features what are the other features in Software Management Functionalities ?
12.What is initialization ?
13.What is Check consistency ?
14.What is background verification ?
15.What is a RAID array ?
16.Whats the difference between a JBOD & a RAID array ?
17.When JBOD is preferred over RAID array ?
18.What is a hot spare ?
19.What is a Logical drive or Virtual drive ?
20.What is rebuilding of array ?
21.What you do when a drive in an array fails, how you bring it back to optimal online mode ?
22.What are the different states an array can be in and explain each state?
23.Explain Online,Offline,Degraded states of an array ?
24.What is the difference between a global hotspare & a dedicated hotspare ?
25.How RAID is configured through BIOS ?
26.HoW RAID is configured in OS level?
27.What is the difference between a software RAID & hardware RAID ?
28.Which is best RAID level for performance and which is best for redundancy?










1.WHAT ARE THE BENEFITS OF FIBRE CHANNEL SANS?

Fibre Channel SANs are the de facto standard for storage networking in the corporate data center because they provide exceptional reliability, scalability, consolidation, and performance. Fibre Channel SANs provide significant advantages over direct-attached storage through improved storage utilization, higher data availability, reduced management costs, and highly scalable capacity and performance.


2.WHAT ENVIRONMENT IS MOST SUITABLE FOR FIBRE CHANNEL SANS?

Typically, Fibre Channel SANs are most suitable for large data centers running business-critical data, as well as applications that require high-bandwidth performance such as medical imaging, streaming media, and large databases. Fibre Channel SAN solutions can easily scale to meet the most demanding performance and availability requirements.

3.WHAT CUSTOMER PROBLEMS DO FIBRE CHANNEL SANS SOLVE?

The increased performance of Fibre Channel enables a highly effective backup and recovery approach, including LAN-free and server-free backup models. The result is a faster, more scalable, and more reliable backup and recovery solution. By providing flexible connectivity options and resource sharing, Fibre Channel SANs also greatly reduce the number of physical devices and disparate systems that must be purchased and managed, which can dramatically lower capital expenditures. Heterogeneous SAN management provides a single point of control for all devices on the SAN, lowering costs and freeing personnel to do other tasks.

4.HOW LONG HAS FIBRE CHANNEL BEEN AROUND?

Development started in 1988, ANSI standard approval occurred in 1994, and large deployments began in 1998. Fibre Channel is a mature, safe, and widely deployed solution for high-speed (1Gb, 2Gb, 4Gb) communications and is the foundation for the majority of SAN installations throughout the world.


5.WHAT IS THE FUTURE OF FIBRE CHANNEL SANS?

Fibre Channel is a well-established, widely deployed technology with a proven track record and a very large installed base, particularly in highperformance, business-critical data center environments. Fibre Channel SANs continue to grow and will be enhanced for a long time to come.The reduced costs of Fibre Channel components, the availability of SAN kits, and the next generation of Fibre Channel (4Gb) are helping to fuel that growth. In addition, the Fibre Channel roadmap includes plans to double performance every three years

6.WHAT ARE THE BENEFITS OF 4GB FIBRE CHANNEL?

Benefits include twice the performance with little or no price increase, investment protection with backward compatibility to 2Gb, higher reliability due to fewer SAN components (switch and HBA ports) required, and the ability to replicate, back up, and restore data more quickly. 4Gb Fibre Channel systems are ideally suited for applications that need to quickly transfer large amounts of data such as remote replication across a SAN, streaming video on demand, modeling and rendering, and large databases. 4Gb technology is shipping today.


7.HOW IS FIBRE CHANNEL DIFFERENT FROM ISCSI?

Fibre Channel and iSCSI each have a distinct place in the IT infrastructure as SAN alternatives to DAS. Fibre Channel generally provides high performance and high availability for business-critical applications, usually in the corporate data center. In contrast, iSCSI is generally used to provide SANs for business applications in smaller regional or departmental data centers.

8.WHEN SHOULD I DEPLOY FIBRE CHANNEL INSTEAD OF ISCSI?

For environments consisting of high-end servers that require high bandwidth or data center environments with business-critical data, Fibre Channel is a better fit than iSCSI. For environments consisting of many midrange or low-end servers, an IP SAN solution often delivers the most appropriate price/performance.



1. Differentiate between DAS-NAS-SAN
2. When NAS is a better option than DAS
3. When SAN is a better option than NAS
4. What are the advantages & disadvantages of each of these product types
(Above are Real Questions asked in a recent interview in one of the Storage test job interview)

Some more interview questions with brief answers

1. Name some of the SAN topologies
point-topoint,arbitrated loop, and switched fabric topologies

2. Whats the need for separate network for storage why LAN can not be used?
LAN hardware and operating systems are geared to user traffic, and LANs are tuned for a fast user response to messaging requests.
With a SAN, the storage units can be secured separately from the servers and totally apart from the user network enhancing storage access in data blocks(bulk data transfers), advantageuos for serverless backups.

3. What are the advantages of RAID ?
“Redundant Array of Inexpensive Disks”
Depending on how we configure the array, we can have the
- data mirrored [RAID 0] (duplicate copies on separate drives)
- striped [RAID 1] (interleaved across several drives), or
- parity protected [RAID 5](extra data written to identify errors).
These can be used in combination to delier the balance of performance and reliability that the user requires.


4. When JBOD's are used ?
“Just a Bunch of Disks”
It is a collection of disks that share a common connection to the server, but don’t include the mirroring,
striping, or parity facilities that RAID systems do, but these capabilities are available with host-based software.

5. Differentiate RAID & JBOD ?

RAID: “Redundant Array of Inexpensive Disks”
Fault-tolerant grouping of disks that server sees as a single disk volume
Combination of parity-checking, mirroring, striping
Self-contained, manageable unit of storage

JBOD: “Just a Bunch of Disks”
Drives independently attached to the I/O channel
Scaleable, but requires server to manage multiple volumes
Do not provide protection in case of drive failure

6. What is a HBA ?
Host bus adapters (HBAs) are needed to connect the server(host) to the storage.

7. What are the advantages of SAN ?

Massively extended scalability
Greatly enhanced device connectivity
Storage consolidation
LAN-free backup
Serverless (active-fabric) backup
Server clustering
Heterogeneous data sharing
Disaster recovery - Remote mirroring
While answering people do NOT portray clearly what they mean & what advantages each of them have, which are cost effective & which are to be used for the client's requirements.


1) What is the difference between RAID 0, RAID 1 and RAID 5?

RAID 0 => Plain striping typically with 24kb, 54kb or 128kb stripe size
RAID 1 => Mirroring
RAID 5 => Stripping with parity

2) Describe in brief the composition of FC Frame?
Start of the Frame locator
Frame header (includes destination id and source id, 24 bytes/6 words)
Data Payload (encapsulate SCSI instruction can be 0-2112 bytes in length)
CRC (error checking, 4 bytes)
End of Frame (1 byte)

3) What is storage virtualization?
Storage virtualization is amalgamation of multiple n/w storage devices into single storage unit.

4) What are the protocols used in physical/datalink and network layer of SAN?
a) Ethernet
b) SCSI
c) Fibre Channel

5) What are the types of disk array used in SAN?
a) JBOD
b) RAID

6) What are different types of protocols used in transportation and session layers of SAN?
a) Fibre Channel Protocol (FCP)
b) Internet SCSI (iSCSI)
c) Fibre Channel IP (FCIP)

7) What is the type of Encoding used in Fibre Channel?
8b/10b, as the encoding technique is able to detect all most all the bit errors

8) How many classes of service are available in Fibre Channel?
7 Classes of service

9) What are the main constrains of SCSI in storage networking?
a) Deployment distance (max. of 25 mts)
b) Number of devices that can be interconnected (16)

10) What is a Fabric?
Interconnection of Fibre Channel Switches

11) What are the services provided by Fabric to all the nodes?
a) Fabric Login
b) SNS
c) Fabric Address Notification
d) Registered state change notification
e) Broadcast Servers

12) What is the difference between LUN and WWN?
LUN: unique number that is assigned to each storage device or partition of the storage that the storage can support.
WWN: 64bit address that is hard coded into a fibre channel HBA and this is used to identify individual port (N_Port or F_Port) in the fabric.

13) What are the different topologies in Fibre Channel?
a) Point-to-Point
b) Arbitrary Loop
c) Switched Fabric Loop

14) What are the layers of Fibre Channel Protocol?
a) FC Physical Media
b) FC Encoder and Decoder
c) FC Framing and Flow control
d) FC Common Services
e) FC Upper Level Protocol Mapping

15) What is zoning?
Fabric management service that can be used to create logical subsets of devices within a SAN. This enables portioning of resources for management and access control purpose.

16) What are the two major classification of zoning?
Two types of zoning are
a) Software Zoning
b) Hardware Zoning

17) What are different levels of zoning?
a) Port Level zoning
b) WWN Level zoning
c) Device Level zoning
d) Protocol Level zoning
e) LUN Level zoning


18) What are the 3 prominent characteristics of SAS Protocol?
a) Native Command Queuing (NCQ)
b) Port Multiplier
c) Port Selector

19) What are the 5 states of Arbitrary Loop in FC?
a) Loop Initialization
b) Loop Monitoring
c) Loop arbitration
d) Open Loop
e) Close Loop

20) How does FC Switch maintain the addresses?
FC Switch uses simple name server to maintain the mapping table

21) What is the purpose of disk array?
Probability of unavailability of data stored on the disk array due to single point failure is totally eliminated.

22) What is disk array?
Set of high performance storage disks that can store several terabytes of data. Single disk array can support multiple points of connection to the network.

23) What is virtualization?
A technique of hiding the physical characteristics of computer resources from the way in which other system application or end user interact with those resources. Aggregation, spanning or concatenation of the combined multiple resources into larger resource pools.

24) What is Multipath I/O?
Fault tolerant technique where by there is more than one physical path between the CPU in the computer systems and its main storage devices through the buses, controllers, switches and other bridge devices connecting them.

25) What is RAID?
Technology that groups several physical drives in a computer into an array that you can define as one or more logical drive. Each logical drive appears to the operating system as single drive. This grouping enhances the performance of the logical drive beyond the physical capability of the drives.

26) What is stripe-unit-size?
It is data distribution scheme that complement s the way operating system request data. Granularity at which data is stored on one drive of the array before subsequent data is stored on the next drive of the array. Stripe unit size should be close to the size of the system I/O request.

27) What is LUN Masking?
A method used to create an exclusive storage area and access control. And this can be achieved bye storage device control program.

28) What is the smallest unit of information transfer in FC?
Frame

29) How is the capacity of the HDD calculated?
Number of Heads X Number of Cylinders X Sectors per track X Sector Size

30) What is bad block reallocation?
A bad sector is remapped or reallocated to good spare block and this information is stored in the internal table on the hard disk drive. The bad blocks are identified during the media test of the HDD as well as during various types of read write operations performed during the I/O tests. Apart from the new generation of HDD comes with a technology called BGMS (background media scan) which continuously scans the HDD media for defects and maps them when the drive is idle (this is performed after the HDD is attached to the system).

Here you get 10 more interview questions for storage area networking
31) What are tow types of recording techniques on the tapes?
a) Linear Recording
b) Helical Scan Recording.

32) What is snap shot?
A snapshot of data object contains an image of data at a particular point of time.

33) What is HSM?
Hierarchical storage management, an application that attempts to match the priority of data with the cost of storage.

34) What is hot-swapping?
Devices are allowed to be removed and inserted into a system without turning off the system.

35) What is Hot-Sparing?
A spare device is available to be inserted into the subsystem operation without having to remove and replace a device.

36) What are different types of backup system?
a) Offline
b) Online
c) Near Line

37) What is the different between mirroring, Routing and multipathing?

Redundancy Functions Relationships Role
Mirroring Generates 2 i/os to 2 storage targets Creates 2 copies of data
Routing Determined by switches independent of SCSI Recreates n/w route after a failure
Multipathing Two initiator to one target Selects the LUN initiator pair to use

38) Name few types of Tape storage?
a) Digital Linear Tape
b) Advanced Intelligent Tape
c) Linear Tape Open

39) What is a sequence in FC?
Group of one or more frames that encompasses one or more “information units” of a upper layer protocol.

Example:
It requires
i) One sequence to transfer the command
ii) One or more sequence to transfer the data
iii) Once sequence to transfer the status.

40) What is Exchange in FC?
Exchange is to establish a relationship between 2 N_PORTs and then these two ports transfer data via one or more sequence within this relationship.
Example: Exchange exist to transfer the command, data and the status of one SCSI task

40) What is Exchange in FC(Fibre Channel)?
Exchange is to establish a relationship between 2 N_PORTs and then these two ports transfer data via one or more sequence within this relationship.
Example: Exchange exist to transfer the command, data and the status of one SCSI task

41) Why do we need Login in FC?
Port Login: To exchange service parameters between N_Ports and N_Ports
Process Login: To establish the SCSI operating environment between two N_PORTS

42) What are the different types of clusters?
a) High availability clusters
b) High Performance Clusters
c) Load Balancing Clusters.

43) What are three levels of management in storage?
a) Storage Level Management
b) Network Level Management
c) Enterprise Level Management.

44) What are the key activities in SAN management?
a) Monitoring
b) Configuring
c) Controlling
d) Troubleshooting
e) Diagnosing

45) What is the difference between HBA and NIC?
HBA => Host bus adapters are used in storage based traffic while NIC (Network Interface Cards are used in IP based LAN traffic.

46) What is the measuring unit of data activity?
Gigabits per hour

47) What are the basic storage policies?
a) Security and authentication
b) Capacity, Content and quota management
c) Quality of Service

48) What is bypass circuitry?
A circuit that automatically removes the storage device from the data path (FC device out of FC AL loop) when signaling is lost (this signal is called port by-pass signal).

49) Explain different classes of service in FC?
Class 1: dedicated connection between two communicators with acknowledgement of frame delivery.
Class 2: is connection less but provides acknowledgement
Class 3: is connection less and provides no notification of delivery
Class 4: allows fractional bandwidth for virtual circuits
Class 5: Provides multicast with acknowledgment
Class F: Is used for switch to switch communication in the fabric.

50) How many connections are possible in Fabric topology?
2^24 (24 bit address to the port) , and the largest possible fabric will have 239 interconnected switches.

51) What is one of the constrains of using storage switch?
Latency

52) What is the difference between NAS and SAN?

NAS
Cables used in the n/w
n/w protocols (TCP/IP, IPx) and file sharing protocols (IFS & NFS)
Lower TCO
Support heterogeneous clients
Slow

SAN
High-speed connectivity such as FC
Do not use n/w protocols because data request are not made over LAN
Higher TCO
Requires special s/w to provide access to heterogeneous clients
Fast

53) What is Jitter?
Jitter refers to any deviation in timing that a bit stream suffers as it traverses the physical medium and the circuitry on-board the end devices. A certain amount of deviation from the original signaling will occur naturally as serial bit stream propagates over fibre-optic or copper cabling.

Mainly caused by electro magnetic interference

54) What is BER/Bit error rate?
Probability that a transmitted bit will be erroneously received is the measure of number of bits (erroneous) at the output of the receiver and dividing by the total number of bits in transmission.

55) What is WWPN?
WWPN is the 16bit character that is assigned to the port, SAN volume controller uses it to uniquely identify the fibre channel HBA that is installed in the host system.

56) What is connection allegiance?
Given multiple connections are established, individual command/response pair must flow over the same connection. This connection allegiance ensures that specific read or writes commands are fulfilled without the additional overhead of monitoring multiple connections and to see whether a particular request is completed.

57) What is burst Length?
The burst length is the number of bytes that the SCSI initiator sends to the SCSI target in the FCP_DATA sequence.

58) Explain different types of RAID?
RAID 0: data striping blocks are written sequentially, no redundancy, high performance than single disk access.

RAID 1: Mirroring, data blocks written to both disk at once, 100% redundancy, 100% additional capacity required. Read can be distributed across both the disks to increase performance.

RAID 3: Striping with byte parity, adds parity information to rebuild data in the event of disk failure, high transfer rate and availability with lower capacity required than RAID 1. Transactions performance low because all disks operate in lock step.

RAID 4: striping with block parity, independently accessible disks, data blocks written sequentially to each disk failure. Dedicated parity disk is write bottleneck and leads to poor performance.

RAID 5: Striping with rotational parity, parity blocks written per row and distributed across all disks, parity distribution eliminates single write bottleneck overhead for parity calculation on write supplemented with parallel microprocessors or caching.

59) What is NAS in detail ?
NAS or Network Attached Storage
“NAS is used to refer to storage elements that connect to a network and provide file
access services to computer systems. Abbreviated NAS. A NAS Storage Element consists of an interface or engine, which implements the file services, and one or more devices, on which data is stored.
NAS elements may be attached to any type of network. When attached to SANs, NAS elements may be considered to be members of the SAS (SAN Attached Storage) class of storage elements.

A class of systems that provide file services to host computers. A host system that uses network attached storage uses a file system device driver to access data using file access protocols such as NFS or CIFS. NAS systems interpret these commands and perform the internal file and device I/O operations necessary to execute them.”

Though the NAS does speed up bulk transfers, it does not offload the LAN like a SAN does. Most storage devices cannot just plug into gigabit Ethernet and be shared - this requires a specialized file server the variety of supported devices is more limited.NAS has various protocols established for such needed features as discovery, access control, and name services.

60)Briefly list the advantages of SAN ?
SANs fully exploit high-performance, highconnectivity network technologies
SANs expand easily to keep pace with fast growing storage needs
SANs allow any server to access any data
SANs help centralize management of storage resources
SANs reduce total cost of ownership (TCO)

1)What is the most critical component in SAN?
2)What is the default id for SCSI HBA?
3)What is parallelism?
4)What do you know about SAN testing?
5)Explain a typical SAN landscape?
6)What is fan-in and fan-out in SAN Virtualization system?
7)How is the interoperability between the server and the storage is achieved?
8)What are the performance metrics of SAN?
9)What do you know about I/O meters , their types and how are the used?
10)What is the equivalent of Address resolution protocol in storage?
11)What is meant by availability & reliability in Storage ?
12)What is Disaster Recovery & how it is implemented in a Storage environment?
13)Example for failover cluster configurations ?
14)What are the needs/advantages of Storage consolidation ?


# Name the mandatory disk group in VxVM 3.5 ? How will you configure VxVM in 3.5 ?
ANS: rootdg is the mandatory disk group in VxVM 3.5, vxinstall is the command to configure VxVM, It will create the disk groups, initializes the disks and adds them to the group.

# How will you create private and shared disk group using VxVM ?
ANS: For Private DG:
Command: vxdg init

For Shared DG:
Command: vxdg -s init < disk1 disk2 disk3 >

# Which are the different layouts for volumes in VxVM ?
ANS: mirror, stripe, concat (default one), raid5, stripe-mirror, mirror-stripe.

# What is the basic difference between private disk group and shared disk group ?
ANS: Private DG: The DG which is only visible for the host on which you have created it, if the host is a part of cluster, the private DG will not be visible to the other cluster nodes.
Shared DG: The DG which is sharable and visible to the other cluster nodes.

# How will you add new disk to the existing disk group ?
ANS: Run vxdiskadm command, which will open menu driven program to do various disk operations, select add disks option or you can use another command vxdiskadd.

# How will you grow/shrink the volume/file system ? What is the meaning of growby and growto options ? What is the meaning on shrinkto and shrinkby options ?
ANS: vxassist command is used to do all volume administration, following is the description and syntax.

Growby option: This is will grow your file system by adding new size to the existing file system.

Growto option: This will grow your file system as per the new size. This WILL NOT ADD new size to the existing one.

Shrinkby option: This will shrink your file system by reducing new size from existing file system.

Shrinkto option: This will shrink your file system as per the new size. This WILL NOT REDUCE the file system by reducing new size.

Command:
vxassist -g [growto, growby, shrinkto, shrinkby] length

# How will you setup and unsetup disks explicitly using VxVM ?
ANS: You can use /etc/vx/bin/vxdiskunsetup to unsetup the disk, and /etc/vx/vxdisksetup to setup the disk.

# How will you list the disks, which are in different disk groups ?
ANS: vxdisk list is the command will list the disks from the DG which is currently imported, you can check the same using vxprint command too. vxdisk -o alldgs list command list all the disks which are in different dg's.

# What is the private region in VxVM ?
ANS: Private region stores the structured VxVM information, it also stores the disk ID and disk geometry. In short words it has metadata of the disk.

# If, vxdisk list command gives you disks status as "error", what steps you will follow to make the respective disks online ?
ANS: If you faced this issue because of fabric disconnection then simply do vxdisk scandisks, otherwise unsetup the disk using using /etc/vx/bin/vxdiskunsetup and setup the disks again using /etc/vx/bin/vxdisksetup, this will definitely help! [ /etc/vx/bin/vxdiskunsetup will remove the private region from the disk and destroys data, backup the data before using this option]




31) How will you set a default router ?
A) # /etc/defaultrouter

32) How to remove all current routes and assign 192.168.1.100 as default router?
A) # route flush
# route add default 192.168.1.100

33) How to change the network settings ?
A) # sys-unconfig

34) What all does the NVRAM store?
A) Ethernet Address / Host ID / Time of Day (TOD) clock and EEPROM Parameters

35) Where are all the port numbers stored?
A) Port numbers are stored in /etc/services

36) Where are eeprom file stored ?
A) /usr/sbin/eeprom

37) Some important NIS commands :
1) # ypcat hosts à Prints info from hosts database
2) # ypmatch host1 hosts à Match individual host entries
3) # ypmatch user1 passwd
4) # ypwhich à Returns NIS master server.

38) Controlling the tape drive ?
1) mt –f /dev/rmt/0n à ‘n’ indicates no rewind.

39) What are the network utilities ?
1) snoop à To capture network packets & display contents
2) netstat –i à Displays state of Ethernet address
3) ndd command à Set & examine kernel parameters namely TCP/IP drivers.

40) Network Configuration :
1) /etc/resolv.conf : Contains Internet domain name, name server and search order.

2) /etc/nsswitch.conf : Specifies information source from files, NIS, NIS+ or DNS

3) /etc/hostname.[int](hme0|eri0|le0] : IP v4 host

4) /etc/nodename : IP v6 host

5) /etc/inet/hosts : Host namefile (/etc/host links to this file)

6) /etc/inet/netmasks : TCP/IP subnet router

7) /etc/inet/protocols : Network protocols

8) /etc/inet/services : Network service name & port numbers

9) /etc/notrouter : Create this file to prevent in.routed or in.rdiscd from starting at boot time

10) /etc/inet/inetd.conf : Internet super daemon config file

11) To change hostname / ip address :

/etc/hostname.{int}(hme0|le0)
/etc/nodename
/etc/inet/hosts
/etc/net/*/hosts
/etc/defaultrouter
/etc/resolv.conf


41) How to configure interfaces at boot time>
A) /etc/rcS.d/s30network.sh file à This script is run each time system is booted. It uses ifconfig utility to configure each interface with IP add & other network info.It searches for files called : hostname.xxn in /etc where xx à int type & nà instance of interface.


11) Which command displays the system configuration information?
A) prtconf

12) Which command is used to configure newly attached hardware ?
A) devfsadm –c where

13) What are the different types of “file systems” in Solaris?
A) There are 3 Types of file system :
13.A.1) Disk based : ufs (standard unix), hsfs (cd-rom), pcfs (Floppy)
Or udf (DVD and CD Rom)
13.A.2) Distributed : NFS (enables sharing of files between many types of n/w)
13.A.3) Pseudo : tmpfs (temporary), swapfs , fdfs, procfs

14) What is a “boot block”?
A) The bootstrap program (bootblk) is found in the next 15 disk sectors. Only the “root” file system has an active boot block, although the space is allocated for boot block at the beginning of each file system.

15) What is “superblock”?
A) The file system is determined by its superblock. It is contained in the 16 disk sectors following the boot block. It contains :
• No. of data blocks
• No.of cylinder groups
• Size of data block fragment
• Description of hardware
• Name of mount point
• File system state flag ( clean , stable , active , logging or unknown)

16) How will you repair the main superblock if it gets corrupted?
A) Every file system has backup superblock at block no.32, which can be given to fsck to repair the main superblock.
# fsck –o b=32 /dev/rdsk/c0t0d0s0

17) How to create new file systems ?
A) newfs /dev/rdsk/c0t0d0s0

18) How will you restore /etc/vfstab file if it gets corrupted?
A) Step 1 : Insert Solaris CD 1 of 2
Step 2 : Go to single user mode : ok boot cdrom –s
Step 3 : Run “fsck” on /(root) partition : # fsck /dev/rdsk/c0t0d0s0
Step 4 : Mount /(root) file system on /a directory to gain access to file system
# mount /dev/dsk/c0t0d0s0 /a
Step 5 : Set & export TERM variable
# TERM=sun
# export TERM
Step 6 : Edit /etc/vfstab file and remove the incorrect entry : # vi /a/etc/vfstab
Step 7 : Unmount the file system : # cd / ; # umount /a and reboot the system.

19) How will you share user’s home directory?
A) Step 1 : Login as root and verify mountd daemon is running
# ps –ef | grep mountd
Step 2 : If the daemon is not running start it :
# /etc/init.d/nfs.server start
Step 3 : List all shared filesystems
# share
Step 4 : Edit the /etc/dfs/dfstab file and add :
# share –F nfs /export/home
Step 5 : Share the file systems in the /etc/dfs/dfstab file :
# shareall –F nfs
Step 6 : Verify that the home directory is shared.
# share

20) What does /etc/inittab file contain ?
A) The /etc/inittab contains the systems default run level, processes to start/monitor
or restart. It also contains the actions to be taken when run level changes.
/etc/inittab file is in foll format :- id:rstate:action:process

1) What files control user administration?
A) /etc/passwd file: 7 Fields: loginid:x:userid:groupid:comment:homedir:shell
/etc/shadow: 9 Fields: loginid:password:lastchng:min:max:warn:inactive:expire
/etc/group : 4 Fields : groupname:password:groupid:username list)

2) What does the “pwconv” command do?
A) It updates the /etc/shadow file with information from /etc/passwd file.

3) Where are the failed login attemps to system logged?
A) /var/adm/loginlog (We need to create this file as it does not exist by default)

4) Which command shows the users currently logged in to system?
A) who ( It reads the information from /var/adm/utmpx file)

5) Which command will show detailed information about a user?
A) finger –m

6) Which command displays all login and logouts?
A) last (It reads the information from /var/adm/wtmpx file)

7) What is the “StickyBit” file permission?
A) Sticky Bit permission protects the file within a public writable directory.
File set with sticky bit will not allow any user to delete the file except the
Owner of file, owner of the group or the root user.

8) How is ACL (Access Control Lists) implemented?
A) 8.1) “getfacl”command : To display an ACL on file.
Syntax : getfacl

8.2) setfacl command : To set the ACL on file
Syntax : setfacl


8.3) setfacl –m command : To modify ACL entries
Syntax : setfacl –m

8.4) setfacl –s command : Remove old ACL entries and replace with new one.
Syntax : setfacl –s

8.5) setfacl –d command : Delete ACL entry
Syntax : setfacl –d

9) Imp “root(/)” subdirectories and their purpose :
9.1) / : Root of overall file system.
9.2) /bin : Symbolic link to /usr/bin. Stores standard system commands and binary files.
9.3) /dev : Primary location for “logical” device names
9.4) /devices : Primary location for “physical” device names
9.5) /etc : Contains host specific system admin config files
9.6) /export : Default directory for commonly shared filesystems.
9.7) /home : Default directory / mount point for user’s home directory
9.8) /kernel : Directory of platform independent loadable kernel file
9.9) /mnt : Temporary mount point for file systems
9.10) /opt : Default directory for add on packages
9.11) /sbin : Executables used in booting process and file recovery
9.12) /tmp : Temporary files
9.13) /usr : Mount point for /usr file system
9.14) /var : Directory for varying files, temporary logging or status files

10) What are the different disk slices?

Slice Name Function
0 / Root’s system files
1 swap Swap area
2 Entire Disk
5 /opt Optional Software
6 /usr System Exe’s
7 /export/home User’s file and directories

1) What files control user administration?
A) /etc/passwd file: 7 Fields: loginid:x:userid:groupid:comment:homedir:shell
/etc/shadow: 9 Fields: loginid:password:lastchng:min:max:warn:inactive:expire
/etc/group : 4 Fields : groupname:password:groupid:username list)

2) What does the “pwconv” command do?
A) It updates the /etc/shadow file with information from /etc/passwd file.

3) Where are the failed login attemps to system logged?
A) /var/adm/loginlog (We need to create this file as it does not exist by default)

4) Which command shows the users currently logged in to system?
A) who ( It reads the information from /var/adm/utmpx file)

5) Which command will show detailed information about a user?
A) finger –m

6) Which command displays all login and logouts?
A) last (It reads the information from /var/adm/wtmpx file)

7) What is the “StickyBit” file permission?
A) Sticky Bit permission protects the file within a public writable directory.
File set with sticky bit will not allow any user to delete the file except the
Owner of file, owner of the group or the root user.

8) How is ACL (Access Control Lists) implemented?
A) 8.1) “getfacl”command : To display an ACL on file.
Syntax : getfacl

8.2) setfacl command : To set the ACL on file
Syntax : setfacl


8.3) setfacl –m command : To modify ACL entries
Syntax : setfacl –m

8.4) setfacl –s command : Remove old ACL entries and replace with new one.
Syntax : setfacl –s

8.5) setfacl –d command : Delete ACL entry
Syntax : setfacl –d

9) Imp “root(/)” subdirectories and their purpose :
9.1) / : Root of overall file system.
9.2) /bin : Symbolic link to /usr/bin. Stores standard system commands and binary files.
9.3) /dev : Primary location for “logical” device names
9.4) /devices : Primary location for “physical” device names
9.5) /etc : Contains host specific system admin config files
9.6) /export : Default directory for commonly shared filesystems.
9.7) /home : Default directory / mount point for user’s home directory
9.8) /kernel : Directory of platform independent loadable kernel file
9.9) /mnt : Temporary mount point for file systems
9.10) /opt : Default directory for add on packages
9.11) /sbin : Executables used in booting process and file recovery
9.12) /tmp : Temporary files
9.13) /usr : Mount point for /usr file system
9.14) /var : Directory for varying files, temporary logging or status files

10) What are the different disk slices?

Slice Name Function
0 / Root’s system files
1 swap Swap area
2 Entire Disk
5 /opt Optional Software
6 /usr System Exe’s
7 /export/home User’s file and directories
--Regards--
Rajeev Mahura
Servers & Storage Professional
http://about.me/rajeevmahura
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