topic Re: raid 5 parity size in Disk Enclosures

raid 5 parity size

saandeep — Thu, 22 Oct 2009 06:14:50 GMT

Hi I emc-cx320 array with Two raid groups both are raid level 5

Raid group0 consist of 5 disks of 133.68 Gb
Raid group1 consist of 10 disks of 133.68 Gb

As RAID 5 is distributed parity, how can we know size of total parity in both Raid groups

Is there any method?

Thanks

Re: raid 5 parity size

Greybeard — Mon, 26 Oct 2009 13:32:35 GMT

Parity in a RAID 5 is the capacity of one disk spread across the array, so each array should use about 133GB for parity, it is an odd/even bit calculation so will make one sum per pass across all disks in the array therefore number of disks makes no difference, N+1 where in your case N=5 or 10.

Re: raid 5 parity size

saandeep — Tue, 27 Oct 2009 13:11:50 GMT

so is there any formula to calculate parity size?

Re: raid 5 parity size

Michal Kapalka (mikap) — Tue, 27 Oct 2009 13:14:01 GMT

hi,

you could use raid calculator

http://www.ibeast.com/content/tools/RaidCalc/RaidCalc.asp

mikap

Re: raid 5 parity size

saandeep — Wed, 28 Oct 2009 06:53:42 GMT

Thanks Michal,

Re: raid 5 parity size

TTr — Wed, 28 Oct 2009 11:41:20 GMT

Parity in RAID5 is EXACTLY the equivalent storage of ONE disk. It does not matter how many total disks are in the group. So group0 is 4D+1P (four data plus one parity) and group1 is 9D+1P

We don't need specialized calculators for every little special case that you come across.