topic Re: RAID 5 in Disk

RAID 5

Darren Murray_1 — Thu, 24 Nov 2005 05:08:24 GMT

Hi there,

I am looking for 2TB available in raid 5.

How many 146gb drives would I need to make this happen, ie how many do I lose as parity disks.

Cheers
Darren

Re: RAID 5

Jefferson Humber — Thu, 24 Nov 2005 06:42:48 GMT

Darren,

Depends, if you want 2000Gb or 2048Gb.

The formula I believe is;

N - 1, where N equals the total number of disk drives in the disk array.

Jeff

P.S This is for vanilla RAID5, not ADG

Re: RAID 5

Vincent Fleming — Thu, 24 Nov 2005 06:48:56 GMT

It depends on which disk array also.

MSA, EVA, or XP?

MSA is variable (N-1) to a point,
EVA is 4D+1P (plus spares),
XP is either 3D+1P or 7D+1P

Re: RAID 5

Ivan Ferreira — Thu, 24 Nov 2005 07:09:11 GMT

In a normal raid you loose one disk for partiy, then you have the spare disks (or spare space in virtual arrays)

In virtual arrays, you don't talk about disks, but space. In virtual arrays you loose 25% of space for RAID + the protection levels (or spare). But, in the eva world, a protection level of "single" consumes the space of two disks.

You should specify if you use virtual arrays (EVA,XP) or not.

Re: RAID 5

Sยภเl Kย๓คг — Thu, 24 Nov 2005 16:29:02 GMT

Hi,
Which is your storage. What is the emulation which you are planning. Are u planning for a 3D+1 on raid 5. What is the lun size?
Post the reply
Regards,
Sunil

Re: RAID 5

Ted Buis — Tue, 29 Nov 2005 21:54:53 GMT

Remember that storage people take 1KB as 1000 bytes, not 1024. That adds up when you get to TB range. Also, there is always file system overhead, so err on the high side. You also need a certain number of drives to get good performance. Get at least 18 drives, to have room and a spare.

Re: RAID 5

Mike Reznak — Wed, 30 Nov 2005 02:42:53 GMT

Hi,
and don't forget to count formated capacity. It's about 6% less than raw capacity.

Mike