topic Re: RAID 5 in Disk Enclosures

RAID 5

Sundar_7 — Thu, 09 Dec 2004 13:48:51 GMT

Just a quick question for you folks.

If add 4 disks of size 146 GB to a XP 1024 array and make it as a RAID 5 group, what would be the effective disk space available for use ?

I guess the answer is 3 * 146 GB = 438 GB, but wanted to confirm.

Re: RAID 5

Pete Randall — Thu, 09 Dec 2004 13:57:34 GMT

That's true - one disk is required to store the parity data so that leaves you with three.
Expressed as a percentage, the various configurations give you:

3 disks: 66%
4 disks: 75%
5 disks: 80%
6 disks: 83%

Pete

Re: RAID 5

Deoncia Grayson_1 — Thu, 09 Dec 2004 14:01:31 GMT

Your answer is correct, you can read this link for better clarification:

http://www.pcguide.com/ref/hdd/perf/raid/levels/singleLevel5-c.html

Re: RAID 5

Zinky — Thu, 09 Dec 2004 14:08:16 GMT

RAID5 Capacity:

CAP=(No of disks -1)* NNN GB per disk

3+1P (75% efficiency - for a 4 isk Array group) yields the best performance on the XP series although for "cerain applcaications" a 7+1P (87.5% efficiency 8 disk Array Group) is the most cost effective.

Re: RAID 5

Sundar_7 — Thu, 09 Dec 2004 14:23:15 GMT

Wonderful ! thanks for the confirmation.