July 23, 2009 at 1:51 pm
Hi EveryOne..
After doing the RAID configuration in SAN , they have divided the drives E & D then they shared to the server . E for Raid level 10 and D for Raid level 51 . I want know whethere this two drives are logical or physical drives ?. Can you expalin me that how will be the Disk io performance and dividing the drive D & E into multiple drive will improve the Disk IO performance ?
Thanks in Advances.
May 7, 2010 at 7:11 am
That question all over the map. Let me try and spell out basics around physical storage.
Drives letter are logical drives. It represents blocks of space that windows identifies are drive letters. In your case drive letters map to one or more LUNs on a SAN. A LUN is a slice of space reserved within a SAN that comprise a set of actual physical drives in some raid configuration.
Think about how a drive physically works. It is not unlike a record player, where a needle jumps to a sector to read or write data from a specific location. The needle can only be in one place at a time, and it takes time for the needle to change places. If you are trying to read and write data on the same drive from multiple places at the same time, then there is going to be time wasted as the needle jumps from one sector to another again and again. If you have sepearate drives or LUNS for each large data file then you can divide the work amongst independent needles and reduce the amount of physical seek time, therefore, disk contention. This is why we separate data, logs, and tempdb files onto separate physical drives, because disk operations can be handled faster using multiple disks.
May 7, 2010 at 9:28 pm
Thank you very much for your reply...
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