Question 
Why is SCSI performance superior to that of IDE/ATA? Explain the reasons from an architectural perspective

Answer :
SCSI offers improved performance and expandability and compatibility  options, making it suitable for high-end computers.
- Number of devices supported is 16
- SCSI architecture derives its base from the client-server relationship
- SCSI initiator, or a client, sends a request to a SCSI target, or a server.
- The target performs the tasks requested and sends the output to the initiator
- When a device is initialized, SCSI allows for automatic assignment of device IDs on the bus, which prevents two or more devices using the same SCSI IDs

Question 
What is a difference between a Cluster and a geographically-dispersed Cluster from administrative perspective?

Answer :
Geographically dispersed clusters, also called stretched clusters or extended clusters, are clusters comprised of nodes that are placed in different physical sites. Geographically dispersed clusters are designed to provide failover in the event of a site loss due to power issues, natural disasters or other unforeseen events.
From administrative perspective the difference would come up due to the storage that will be used. It won't be a common storage available at the respective locations instead a replication between the two will have to be set up and managed accordingly. Managing failover will also be different than a normal
cluster.

Question
DAS provides an economically viable alternative to other storage networking Solutions. Justify this statement

Answer :
- Setup requires a relatively lower initial investment
- Setup is managed using host-based tools, such as the host OS, which makes storage management tasks easy for small and medium enterprises.
- Requires fewer management tasks, and less hardware and software elements to set up and operate.

Question

i.Write the type of networks in place of N1 and N2. Write the type of ports in place of P1 and P2.
ii. What is meant by FC network is lossless? How FC achieve this ? How can we achieve losslessness in FCoE?

Answer
(i)N1 – IP Network. N2 – FC SAN. P1- Native SCSI port. N2- FC port

(ii) An FC network is lossless, meaning that the protocol has a built-in mechanism that prevents frame drops caused by congestion. Fibre Channel manages congestion through link level, credit based flow control. With credit-based flow control, the receiver sends credits to the sender to indicate the availability of receive buffers; the sender waits for credits before transmitting messages to the receiver Busy receive port can send the control frame to the transmit port for pause in transmission. This is called PAUSE capability of ethernet. Using this FCoE supports losslessness which is required in FC transmission.
Question 
We have 6 nodes running a cluster. If suddenly 5 nodes found that they can communicate with each other but they cannot communicate with one specific node.
i. What steps the cluster should take to prevent data corruption? What is this phenomena called?
ii. Now if it is found that cluster is split in two groups with 3 nodes in each group. Nodes in one group can communicate with each other but can not communicate with nodes of other group. What is this situation called? Explain in brief about the steps the cluster will take to resolve the problem. 
Answer :
(i) The node will be forced to shut down through some managed Switch. This is called fencing.
(ii)This is called as split brain. To prevent data corruption cluster should shut down the group with lesser number of nodes. Since here the number of nodes are equal, cluster will take the help of quorum disk to decide the group of nodes to be shut down

Question
A host generates 8,000 I/Os at peak utilization with an average I/O size of 32 KB.  The response time is currently measured at an average of 12 ms during peak utilizations. When synchronous replication is implemented with a Fiber Channel ink to a remote site, what is the response time experienced by the host if the network latency is 6 ms per I/O?

Answer :
Actual response time = 12+ (6*4) + (32*1024/8000) = 40.096
Where 12 ms = current response time
6 ms per I/O = latency
                   32*1024/8000 = data transfer time

Question 
It is required to connect one FOCE SAN and one FC SAN to a rack mounted servers having 10Gbe CNAs. Suggest a plan of connection with a diagram showing necessary components.

Answer :

Question 
Explain the action involved between the NDMP DMA control and NDMP Server during Recovery process in the given scenario.

Answer :

DMA creates a control connection to the secondary storage agent
 Connect using TCP port 10,000
 NDMP_CONNECT_OPEN  (to negotiate version)
 NDMP_CONNECT_CLIENT_AUTH (to authenticate DMA to Server)
DMA uses the tape library media changer to load the required tape
The SCSI service is invoked
 NDMP_SCSI_OPEN
 NDMP_SCSI_EXECUTE_CDB - to manipulate media changer
NDMP_SCSI_CLOSE
DMA prepares the tape service for a recovery operation
 The tape service is invoked
 NDMP_TAPE_OPEN
 NDMP_TAPE_READ - to validate volume label
 NDMP_TAPE_MTIO - to position tape to start of backup data
DMA prepares the mover for a recovery operation
 The mover is invoked
 NDMP_MOVER_SET_RECORD_SIZE
 NDMP_MOVER_SET_WINDOW
  DMA opens control connection to the primary storage agent
 Connect using TCP port 10,000
 NDMP_CONNECT_OPEN - to negotiate protocol version
 NDMP_CONNECT_CLIENT_AUTH - to authenticate DMA to Server
  DMA queries secondary storage agent for capabilities
 NDMP_CONFIG_GET_CONNECTION_TYPE
  DMA queries primary storage agent for capabilities
 NDMP_CONFIG_GET_BUTYPE_INFO
 NDMP_CONFIG_GET_CONNECTION_TYPE
  DMA obtains the data server’s data connection address information
 The Data service is invoked
 NDMP_DATA_LISTEN
  DMA creates a data connection connection between NDMP servers
 NDMP_MOVER_CONNECT
  DMA creates a data connection connection between NDMP servers
 The mover connects to the specified IP address & TCP port
  DMA instructs the data server to initiate the recovery operation
 NDMP_DATA_START_RECOVER
  DMA recovery request is processed
 Data service determines the offset & length of the DMA specified recovery data
 Data server requests the specified data stream be transferred
 NDMP_NOTIFY_DATA_READ
  DMA instructs the mover to transfer the specified recovery stream
 NDMP_MOVER_READ
the mover interacts with the tape service to access the recovery stream
  DMA instructs the mover to transfer the specified recovery stream
 The mover begins sending recovery stream over data connection
  NDMP Data & Tape services send periodic log messages to DMA
 NDMP_LOG_MESSAGE
  NDMP Tape service sends notification when DMA intervention is required
example: end of mover window or tape medium encountered
 NDMP_NOTIFY_MOVER_PAUSED
  DMA initiates tape swap possibly utilizing media changer support
 NDMP_TAPE_MTIO - to rewind/unload tape
 NDMP_SCSI_EXECUTE_CDB - to manipulate media changer
 NDMP_TAPE_MTIO - to position new tape
 NDMP_TAPE_READ - to validate new tape header
DMA prepares the mover to continue the recovery operation
 NDMP_MOVER_SET_WINDOW
 NDMP_MOVER_CONTINUE
Data server detects end of recovery operation

Note: We have tried solving the question paper in a very short time span as per our understanding and the study material we had. Feel free to contact us through comment box or through email if you have some descriptive answer.



Question) 
Answer)
In a wide SCSI, the device IDs from 8 to 15 have the highest priority, but the entire sequence of wide SCSI-IDs has lower priority than narrow SCSI IDs.

Therefore, the overall priority sequence for a wide SCSI is 7, 6, 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, and 8.

Question) Firewall configuration is difficult for which NFS version? Justify.
Answer)
NFS is a client server protocol that allows users to share files across a network. There are some problems with NFS as stated below:
● NFS relies on the inherently insecure UDP protocol
● Transactions between host and client are NOT encrypted
● Hosts and users cannot be easily authenticated, IP Spoofing is possible
● Persmissions are granted by normal access rules
● Firewall configuration is difficult because of the way NFS daemons work

NFSv3 requires dynamic ports between the NFS server and client which can cause problems getting through your firewall.

Question)
What are the three types of nodes maintained by JFFS2? Mention percentage hit by ‘Garbage Collector’ to reclaims space from various types of nodes.
Answer)
JFFS is a log structured file system, Nodes containing data and metadata are stored on the flash chips sequentially. There are three types of nodes defined and implemented by JFFS2. These are as follows:

1. JFFS2_NODETYPE_INODE - It contains all the inode metadata, as well as potentially a range of data belonging to the inode. However, it no longer contains a file name or the number of the parent inode.
2. JFFS2_NODETYPE_DIRENT - this node represents a directory entry, or a link to an inode. It contains the inode number of the directory in which the link is found, the name of the link and the inode number of the inode to which the link refers. 
3. JFFS2_NODETYPE_CLEANMARKER -- this node is written to a newly erased block to show that the erase operation has completed successfully and the block may safely be used for storage.

Garbage Collector (GC):
Samba is an open-source software suite that runs on Unix/Linux based platforms but is able to communicate with Windows clients like a native application. So Samba is able to provide this service by employing the Common Internet File System (CIFS).

Can we install on windows ? - No we can not install it on Windows. Samba can be run on many different platforms including Linux, Unix, OpenVMS and operating systems other than Windows and allows the user to interact with a Windows client or server natively. It can basically be described as the Standard Windows interoperability suite of programs for Linux and Unix.

Name of file to configure SAMBA: smb.conf

Question )
In a SCSI based interface, a target has to support multiple initiators. Explain how a target will handle an incoming read request when it is busy, giving complete steps of read request between such initiator and a target components (handling multiple imitators) of a SCSI interface. Clearly indicate any assumptions made.

Answer)
Assumptions :Let us assume we have one target T1 and three initiators I1, I2 and I3 with below SCSI IDs :

Initiator  SCSI ID
I1              6
I2              3
I3              5

The device with SCSI ID 7 has the highest priority on the SCSI bus and is usually assigned to the host adapter. The priority of other SCSI IDs is descending from 6 to 0.

Phases of SCSI bus :
There are basically 3 phases :
•Bus Free Phase
–Bus is not being used by anyone

•Arbitration Phase
–One or more initiators request use of the bus and
the one with the highest priority (SCSI ID order) is allowed to proceed

•Selection / Re-selection phase
–Initiator asserts BUS BUSY signal and
•places target’s address on the bus thus establishing a connection/session
–Re-selection applies for a target resuming an interrupted operation:
•target asserts BUS BUSY signal and places initiator’s address on the bus.

Steps for Bus Phase Sequence Read Operation

Question
Which of the following RAID levels gives maximum usable capacity?

Select one:
A. RAID 0
B. RAID 5
C. RAID 6
D. RAID 1

The correct answer is:  RAID 0

Question
Which logical operation is used for computing parity?

Select one:
A. Exclusive OR
B. Exclusive NOR
C. Inclusive NOR
D. Inclusive OR

The correct answer is: Exclusive OR

Question
Which of the following RAID implementation does not allow data recovery in case of disk failure?

Select one:
A. RAID 5
B. RAID 1
C. RAID 0
D. RAID 10

The correct answer is: RAID 0

Question
What is a hot Spare?

Select one:
A. It is a spare drive within a RAID array.
B. It is a drive that can be plugged in while the Storage array is powered on
C. It is an extra drive provided by the vendor to be plugged in in case of disk failure
D. It is a disk that is over heated

The correct answer is: It is a spare drive within a RAID array.

Question
What is a blast zone in RAID?

Select one:
A. It is the portion of disk burnt due to overheating
B. It is the area of impact when data is lost from a failed RAID set.
C. It is the portion platter damaged due to head crash
D. It is the area of impact when the disk explodes.

The correct answer is: It is the area of impact when data is lost from a failed RAID set.

Question
Which of the following statement is true for RAID 5?

Select one:
A. RAID 5 uses block level striping with distributed parity
B. RAID 5 is a hybrid of mirror sets and stripe sets
C. RAID 5 uses block level striping with double distributed parity
D. RAID 5 uses block level striping with a dedicated parity drive

The correct answer is: RAID 5 uses block level striping with distributed parity

Question
Journaling is preferred for

Select one:
A. Storing metadata
B. Storing logs
C. Faster file system recovery
D. Faster write operation

The correct answer is: Storing Faster file system recovery

Question
Examples of Journaling file system

Select one:
A. JFS
B. Ext2
C. Ext3
D. UFS

The correct answer is: Ext3

Question
Wear leveling affects

Select one:
A. RAM
B. Optical storage
C. Hard disk
D. Flash

The correct answer is: Flash

Question
Every File or directory has unique

Select one:
A. Inode
B. Directory
C. Pathname
D. Inode & pathname

The correct answer is: Inode & pathname

Question
Which of the following is not a non volatile storage device?

Select one:
a. Hard Disk
b. Memory Stick
c. NVRAM
d. Random Access Memory

The correct answer is: Random Access Memory

Question
Solid State devices are best suited for ______________ writes & _________________ reads.

Select one:
A. Frequent Random, Frequent Sequential
B. Frequent Sequential, Infrequent Random
C. Infrequent Sequential , Frequent Random
D. Infrequent Random, Frequent Sequential

The correct answer is: Infrequent Sequential , Frequent Random

Question
Which of the following is sequential access storage device?

Select one:
A. CD-ROM
B. Main Memory
C. Hard Disk
D. Tape Cartridge

The correct answer is: Tape Cartridge

Question
A “Logical Volume Manager” helps in

Select one:
A. Virtualizing storage
B. provide direct access to the underlying storage
C. Manage disk space efficiently without having to know the actual hardware details
D. Both storage virtualization and efficient disk space management

The correct answer is: Both storage virtualization and efficient disk space management

Question
Physical Volumes are

Select one:
A. None of these mentioned
B. Disk or disk partitions used to construct logical volumes
C. The space on a physical storage that represent a logical volume
D. A bunch of disks put together that can be made into a logical volume

The correct answer is: Disk or disk partitions used to construct logical volumes

Question
Which of the following are true. Logical Volumes _____

Select one:
A. Can span across multiple volume groups
B. Can span across multiple physical volumes
C. Can be constructed only using a single physical disk
D. None these mentioned

The correct answer is: Can span across multiple physical volumes

Question
Fileystem is created using command

Select one:
A. Mkfs
B. Fsck
C. defrag
D. Format

The correct answer is: Mkfs

Question
Concatenation is the technique of

Select one:
A. Increasing the size of a volume by adding more disks
B. Adding physical volumes together to make a volume group
C. writing a block of data onto one disk and then a block onto another disk in an alternate fashion
D. Filling up a physical volume completely before writing to the next one in a logical volume

The correct answer is: Filling up a physical volume completely before writing to the next one in a logical volume

Question
A MySQL database is involved in persisting random writes to the storage medium quantified by Kilobytes of block data. Which of the below is the suitable metric to measure the performance of the disk operations

Select one:
A. Input Output Operations Per Second
B. Mega Bytes Per Second

The correct answer is: Input Output Operations Per Second

Question
Which of the below attributes to the latency in the data transfer between application and storage Hard disks?

Select one:
A. Head Seek Time between the Platters
B. None of these
C. Cache Miss
D. Disk Controller Queuing

The correct answer is: Cache Miss

Question
MLC has _______________ PE cycles and _______________ in performance compared to SLC SSDs. Where - MLC- MultiLevelCell  ; SLC-SingleLevelCell

Select one:
A. More, Low
B. Less , Low
C. Less , High
D. More ,High

The correct answer is: Less, Low

Question
In a Flash Memory, how is the content of a cell changed to 1 from 0?

Select one:
A. By erasing the content of the cell
B. By block erase operation and rewriting the content of the block
C. By writing 1 to the cell
D. By erasing the content of the cell before writing 1

The correct answer is:  By block erase operation and rewriting the content of the block

Question
Which of the following statement is true for a Single Level Cell?
Select one:
A. It has the longest life span
B. It allows more data storage
C. Singe level cells are cheap
D. It offers medium performance as compared to other formats

The correct answer is: It has the longest life span

Question
Which of the following is applicable to Enterprise class solid state devices?

Select one:
A. They have more over provisioned capacity
B. Warranty terms are same as all Solid state devices
C. They have the simple controller firmware
D. They have same amount of cache is not less than consumer class devices

The correct answer is: They have more over provisioned capacity

Question
Which of the following statement is true about Striping?

Select one:
A. A stripe is stored on a single disk
B. Striping reduces the disk performance
C. Striping helps in data recovery
D. Striping parallelises I/O operation

The correct answer is: Striping parallelises I/O operation

Question
Do iSCSI storage mandatory to required switch?

Select one:
Yes
No
None
a & b both

The correct answer is: No

Question
Best I/O Technique for low volume data transfer

Select one:
Polling
Interrupt Driven
DMA
b and c

The correct answer is: Interrupt Driven

Question
What is the memory bandwidth requirement of a machine executing 4*105 instructions per second, average instruction size of 3.8 bits and 7.2 bits of average operand size per instruction?

Select one:
1.52 Mbps
0.72 Mbps
2.88 Mbps
4.4 Mbps

The correct answer is: 4.4 Mbps

Question
Which version of NFS Mandates strong security

Select one:
NFSv1
NFSv2
NFSv3
NFSv4

The correct answer is: NFSv4

Question
Estimate the sustained transfer rate of a drive if disk drive spins at 7200 RPM, has a sector size of 512 bytes, and holds 160 sectors per track around

Select one:
9400 KB/s
9600 KB/s
9800 KB/s
10000 KB/s

The correct answer is: 9800 KB/s

Question
Which storage Technology uses low level disk drive access commands like READ block, WRITE block and READ capacity

Select one:
NAS
SAN
DAS
All the above

The correct answer is: SAN

Question
How do we meet memory bandwidth requirements?

Select one:
L1 cache, L2 cache and DRAM
Direct Attached Storage and Network Storage
Archival Storage
All the above

The correct answer is: All the above

Question
PCI Bus Lines contains

Select one:
Control Lines
Data Lines
Address Lines
All the above

The correct answer is: All the above

Question
How many disk failure can disk failure can be withstood by RAID 6?

Select one:
1
2
3
4

The correct answer is: 2

Question
Which of the following model makes the server to keep track of cached copies and notifies them on update

Select one:
Asynchronous writing model
Cache verification model
Callback model
Leasing model

The correct answer is: Callback model

Question
What is the capacity of the disk with 5 platters. 2 surfaces per platter, 20000 tracks per surface, 300 sectors per track and 512 bytes per sector

Select one:
30.72GB
24.40GB
21.40GB
15.16GB

The correct answer is: 30.72GB

Question
If average latency is 2.99 ms and average seeks time is 4.7 ms, then IOPS of the disk will be?

Select one:
129
130
128
131

The correct answer is: 130

Question
A certain hard disk has 16 cylinders, 480 tracks per cylinder, 32 sectors per track, and 512 bytes per sector. What is its storage capacity?

Select one:
125,829,120 bytes
125,929,120 bytes
125,729,120 bytes

125,629,120 bytes

The correct answer is: 125,829,120 bytes

Question
If MTTF of  a disk is 80000hrs what us MTTF of an array of 8 disks

Select one:
640000 hrs
10000 hrs
80000 hrs
40000 hrs

The correct answer is: 10000 hrs

Question
Identify a network file protocol in the below mentioned set

Select one:
FC
CIFS
SCSI
NAS

The correct answer is: CIFS

Question
Which option is dedicated for file sharing?

Select one:
bimodal
network attached storage
stealth
storage area network

The correct answer is: network attached storage

Question
If read and write performance is the only criterion, which would you choose?

Select one:
RAID 0
RAID 1
RAID 5
RAID 50

The correct answer is: RAID 0

Question
Which of the following RAID levels guarantees double disk failure protection?

Select one:
Raid 5
Raid 6
Raid 0+1
Raid 1+0

The correct answer is: Raid 6

Question
In SAN network which type of switch used typically?

Select one:
Director switch
Intelligent switch
IP switch
Hub

The correct answer is: Intelligent switch

Question
What is the major function of backup?

Select one:
1. To archive old files
2. To archive sensitive files and emails
3. To be able to recovery data to a point in time
4. To roll an application back up to a previous time

The correct answer is: To be able to recovery data to a point in time

Question
What kind of backup allows a system to be backed up without being shut down?

Select one:
1. Hot backup
2. Warm backup
3. Frozen backup
4. Cold Backup

The correct answer is: Hot backup

Question
The amount of time it takes to recover a system is referred to as what?

Select one:
1. Recovery Time Objective (RTO)
2. Recovery Point Objective (RPO)
3. Recovery Method Objective (RMO)
4. Recovery Objective (RO)

The correct answer is: Recovery Time Objective (RTO)

Question
MLC has _______________ PE cycles and _______________ in performance compared to SLC SSDs. Where - MLC- MultiLevelCell  ; SLC-SingleLevelCell

Select one:
A. More, Low
B. Less , Low
C. Less , High
D. More ,High

The correct answer is: Less , Low

Question
Which of the following capacity optimization technologies is being described: Space is allocated to volumes on-demand as data is written to the volume?

Select one:
1. Deduplication
2. Compression
3. Auto-tiering
4. Thin Provisioning

The correct answer is: Thin Provisioning

Question
Which of the following describes a “backup window”?

Select one:
1. Period of time during which server and application backups can occur
2. Period of time during which data can be restored
3. Period of time during which server and application upgrades can take place
4. Period of time when servers are shutdown so that they can be backed up

The correct answer is: Period of time during which server and application backups can occur

Question
What is a common factor influencing the need for archiving?

Select one:
1. Simplicity of implementation
2. Legislation
3. Performance
4. Cost

The correct answer is: Legislation

Question
Which of the following is not commonly a trait of a snapshot?

Select one:
1. Space efficient
2. Point in Time copy
3. Pointer based
4. Full block copy

The correct answer is: Full block copy

Question
What kind of scenarios does storage replication assist in recovery from?

Select one:
1. User accidentally deleting data
2. Virus
3. Power failures and natural disasters
4. Replication data corruption

The correct answer is: Power failures and natural disasters

Question
What kind of backup backs up data over the SAN without data passing through the app server?

Select one:
1. LAN-free backup
2. WAN backup
3. LAN based backup
4. Serverless backup

The correct answer is: Serverless backup

Question
What physical component does a host need in order to connect to a FC SAN?
Select one:
1. HBA
2. HCA
3. LOM NIC
4. ToE NIC

The correct answer is: HBA

Question
Which of the following is a benefit of storage virtualization?

Select one:
1. Simplified storage management
2. Reduced number of storage arrays
3. Increased capacity
4. Increased support levels

The correct answer is: Simplified storage management

Question
Which of the following replication technologies offer guaranteed zero data loss if recovering from a replica volume?

Select one:
1. Asynchronous replication
2. Synchronous replication
3. Application layer replication
4. Three site cascade topology

The correct answer is: Synchronous replication

Question
What is the most common technique used for finding duplicate blocks/data?

Select one:
1. Encryption
2. Hashing/fingerprinting
3. Storing all blocks in an content addressable object store
4. Bit-for-bit comparisons on all new blocks

The correct answer is: Hashing/fingerprinting

Question
Which capacity optimization technology is being described: Recognizing blocks of data already stored, and only storing a single copy?

Select one:
1. Tiering
2. Compression
3. Over-provisioning
4. Deduplication

The correct answer is: Deduplication

Question
Which protocol does Fibre Channel Protocol encapsulate on a FC SAN?

Select one:
1. SAS
2. ATA
3. iSCSI
4. SCSI

The correct answer is: SCSI

Question
Which of the following effectively describes capacity optimization technologies?

Select one:
1. Technologies used to improve the performance of data stored on disk
2. Technologies used to reduce the space required to store persistent data
3. Technologies used to duplicate stored data
4. Technologies used to reduce the power consumed by media used to store data

The correct answer is: Technologies used to reduce the space required to store persistent data

Question
Logical volume managers are examples of what type of storage virtualization?

Select one:
1. Out-of-band virtualization
2. Host based virtualization
3. Controller based virtualization
4. Network based virtualization

The correct answer is: Host based virtualization

Question
How do devices on an iSCIS SAN learn about topology changes and the likes?

Select one:
1. State Change Notifications
2. Discovery Domains
3. Network broadcasts
4. Rescanning the bus

The correct answer is: Discovery Domains

Question
What is a potential advantage of array based replication over and above hypervisor and application based replication?

Select one:
1. More tightly integrated with applications
2. Offloads replication work from the host
3. Requires smaller replication links
4. Requires less hardware

The correct answer is: Offloads replication work from the host

Question
Which technology allows administrators to allocate more storage than they actually have?

Select one:
1. Right-provisioning
2. Over-provisioning
3. Under-provisioning
4. Thick-provisioning