Monday, 20 February 2017

Frequently Asked SAN – Storage Area Networks interview Questions and Answers

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

12. 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

13. What is FICON ?
FICON is a protocol that uses Fibre Channel as its physical medium. FICON channels are capable of data rates up to 200 MBps full duplex, they extend the channel distance (up to 100 km), increase the number of control unit images per link, increase the number of device addresses per control unit link, and retain the topology and switch management characteristics of ESCON.

14. What is FSPF ?
FSPF keeps track of the links on all switches in the fabric and associates a cost with each link. The cost is always calculated as being directly proportional to the number of hops. The protocol computes paths from a switch to all other switches in the fabric by adding the cost of all links traversed by the path, and choosing the path that minimizes the cost.

15. How FSPF works
The collection of link states (including cost) of all switches in a fabric constitutes the topology database (or link state database). The topology database is kept in all switches in the fabric, and they are maintained and synchronized to each other. There is an initial database synchronization, and an update mechanism.
82 Introduction to Storage Area Networks .The initial database synchronization is used when a switch is initialized, or when an ISL comes up. The update mechanism is used when there is a link state change. This ensures consistency among all switches in the fabric.

16. What is Network Attached Storage (NAS) ?
Network Attached Storage (NAS) is basically a LAN-attached file server that serves files using a network protocol such as Network File System (NFS). NAS is a term used to refer to storage elements that connect to a network and provide file access services to computer systems. A NAS storage element consists of an engine that implements the file services (using access protocols such as NFS or CIFS), and one or more devices, on which data is stored. NAS elements may be attached to any type of network. From a SAN perspective, a SAN-attached NAS engine is treated just like any other server, but a NAS does not provide any of the activities that a server in a server-centric system typically provides, such as e-mail, authentication, or file management.

17. How is Fiber 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.

18. What is Frames?
Fibre Channel places a restriction on the length of the data field of a frame at 528 transmission words, which is 2112 bytes. (See Table 3-2 on page 52.) Larger amounts of data must be transmitted in several frames. This larger unit that consists of multiple frames is called a sequence. An entire transaction between two ports is made up of sequences administered by an even larger unit called an exchange.
A frame consists of the following elements:
_ SOF delimiter
_ Frame header
_ Optional headers and payload (data field)
_ CRC field
_ EOF delimiter

19. What is Loop address ?
An NL_Port, like an N_Port, has a 24-bit port address. If no switch connection exists, the two upper bytes of this port address are zeroes (x’00 00’) and referred to as a private loop. The devices on the loop have no connection with the outside world. If the loop is attached to a fabric and an NL_Port supports a fabric login, the upper two bytes are assigned a positive value by the switch. We call this mode a public loop.

20. What is LUN?
LUN unique number that is assigned to each storage device or partition of the storage that the storage can support

Read More Questions:
SAN Interview Questions Part1
SAN Interview Questions Part2
SAN Interview Questions Part3
SAN Interview Questions Part4
SAN Interview Questions Part5

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