SAN Interview Questions and Answers
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.
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.
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 (1 GB, 2 GB, 4 GB) communications and is the foundation for the majority of SAN installations throughout the world.
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 (1 GB, 2 GB, 4 GB) 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 high-performance, 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 (4 GB) are helping to fuel that growth. In addition, the Fibre Channel roadmap includes plans to double performance every three years.
Fibre Channel is a well-established, widely deployed technology with a proven track record and a very large installed base, particularly in high-performance, 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 (4 GB) 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 2 GB, higher reliability due to fewer SAN components (switch and HBA ports) required, and the ability to replicate, back up, and restore data more quickly. 4 GB 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. 4 GB technology is shipping today.
Benefits include twice the performance with little or no price increase, investment protection with backward compatibility to 2 GB, higher reliability due to fewer SAN components (switch and HBA ports) required, and the ability to replicate, back up, and restore data more quickly. 4 GB 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. 4 GB 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.
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.
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.
9. Name some of the
SAN topologies?
Point-to-point,
arbitrated loop, and switched fabric topologies
10. What’s the need for
separate network for storage why LAN cannot 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), advantageous for server-less backups.
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), advantageous for server-less backups.
11. 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 1] (duplicate copies on separate drives)
- striped [RAID 0] (interleaved across several drives), or
- parity protected [RAID 5](extra data written to identify errors).
These can be used in combination to deliver the balance of performance and reliability that the user requires.
Depending on how we configure the array, we can have the
- data mirrored [RAID 1] (duplicate copies on separate drives)
- striped [RAID 0] (interleaved across several drives), or
- parity protected [RAID 5](extra data written to identify errors).
These can be used in combination to deliver the balance of performance and reliability that the user requires.
12. Define RAID? Which
one you feel is good choice?
RAID (Redundant array of Independent Disks) is a technology to achieve redundancy with faster I/O. There are Many Levels of RAID to meet different needs of the customer which are: R0, R1, R3, R4, R5, R10, R6.
Generally customer chooses R5 to achieve better redundancy and speed and it is cost effective.
R0 – Striped
set without parity/ [Non-Redundant Array].
Provides improved
performance and additional storage but no fault tolerance. Any disk failure
destroys the array, which becomes more likely with more disks in the array. A
single disk failure destroys the entire array because when data is written to a
RAID 0 drive, the data is broken into fragments. The number of fragments is
dictated by the number of disks in the drive. The fragments are written to
their respective disks simultaneously on the same sector. This allows smaller
sections of the entire chunk of data to be read off the drive in parallel,
giving this type of arrangement huge bandwidth. RAID 0 does not implement error
checking so any error is unrecoverable. More disks in the array means higher
bandwidth, but greater risk of data loss
R1 - Mirrored
set without parity.
Provides fault
tolerance from disk errors and failure of all but one of the drives. Increased
read performance occurs when using a multi-threaded operating system that supports
split seeks, very small performance reduction when writing. Array continues to
operate so long as at least one drive is functioning. Using RAID 1 with a
separate controller for each disk is sometimes called duplexing.
R3 - Striped
set with dedicated parity/Bit interleaved parity.
This mechanism
provides an improved performance and fault tolerance similar to RAID 5, but
with a dedicated parity disk rather than rotated parity stripes. The single
parity disk is a bottle-neck for writing since every write requires updating
the parity data. One minor benefit is the dedicated parity disk allows the
parity drive to fail and operation will continue without parity or performance
penalty.
R4 - Block
level parity.
Identical to RAID
3, but does block-level striping instead of byte-level striping. In this setup,
files can be distributed between multiple disks. Each disk operates
independently which allows I/O requests to be performed in parallel, though
data transfer speeds can suffer due to the type of parity. The error detection
is achieved through dedicated parity and is stored in a separate, single disk
unit.
R5 - Striped
set with distributed parity.
Distributed parity
requires all drives but one to be present to operate; drive failure requires
replacement, but the array is not destroyed by a single drive failure. Upon
drive failure, any subsequent reads can be calculated from the distributed
parity such that the drive failure is masked from the end user. The array will
have data loss in the event of a second drive failure and is vulnerable until
the data that was on the failed drive is rebuilt onto a replacement drive.
R6 - Striped
set with dual distributed Parity.
Provides fault
tolerance from two drive failures; array continues to operate with up to two
failed drives. This makes larger RAID groups more practical, especially for
high availability systems. This becomes increasingly important because
large-capacity drives lengthen the time needed to recover from the failure of a
single drive. Single parity RAID levels are vulnerable to data loss until the
failed drive is rebuilt: the larger the drive, the longer the rebuild will
take. Dual parity gives time to rebuild the array without the data being at
risk if one drive, but no more, fails before the rebuild is complete.
13. What is the
difference between RAID 0+1 and RAID 1+0?
RAID 0+1 (Mirrored
Stripped)
In this RAID level
all the data is saved on stripped volumes which are in turn mirrored, so any
disk failure saves the data loss but it makes whole stripe unavailable. The key
difference from RAID 1+0 is that RAID 0+1 creates a second striped set to
mirror a primary striped set. The array continues to operate with one or more
drives failed in the same mirror set, but if drives fail on both sides of the
mirror the data on the RAID system is lost. In this RAID level if one disk is
failed full mirror is marked as inactive and data is saved only one stripped
volume.
RAID 1+0 (Stripped
Mirrored)
In this RAID level
all the data is saved on mirrored volumes which are in turn stripped, so any
disk failure saves data loss. The key difference from RAID 0+1 is that RAID 1+0
creates a striped set from a series of mirrored drives. In a failed disk
situation RAID 1+0 performs better because all the remaining disks continue to
be used. The array can sustain multiple drive losses so long as no mirror loses
both its drives.
This RAID level is
most preferred for high performance and high data protection because rebuilding
of RAID 1+0 is less time consuming in comparison to RAID 0+1.
14. 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.
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.
15. 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”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
Drives independently attached to the I/O channel
Scalable, but requires server to manage multiple volumes
Do not provide protection in case of drive failure.
16. What is a HBA?
Host bus adapters (HBAs) are needed to connect the server (host) to the storage.
Host bus adapters (HBAs) are needed to connect the server (host) to the storage.
17. What are the
advantages of SAN?
Massively extended scalability
Greatly enhanced device connectivity
Storage consolidation
LAN-free backup
Server-less (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.
Massively extended scalability
Greatly enhanced device connectivity
Storage consolidation
LAN-free backup
Server-less (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.
18. What is the
difference 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
The basic difference between SAN and NAS, SAN is Fabric based and NAS is Ethernet based.
SAN - Storage Area Network
It accesses data on
block level and produces space to host in form of disk.
NAS - Network
attached Storage
It accesses data on
file level and produces space to host in form of shared network folder.
19. 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 business following are essentials components of SAN
- Fabric Switch
- FC Controllers
- JBOD's
- Fabric Switch
- FC Controllers
- JBOD's
20. Can you briefly
explain each of these Storage area components?
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