On Wednesday 12 November 2008, lee <lee@yun.yagibdah.de> wrote about 'Re: What is the point of RAID?': >On Wed, 12 Nov 2008 09:44:47 -0500 > >Henning Follmann <hfollmann@itcfollmann.com> wrote: >> Jeff, >> you math is off - way off. > >Well, the problem is that the more drives you have, the more can fail. > >So what is the optimal number of disks in a raid 5 and a raid 1? If by optimal, you mean, least chance of failure: raid-1 = aleph-sub-naught. -- more drives, the better, but you gain no space with each successive drive. raid-5 = 3. -- As you add more drives you get more usable space, but gain no extra redundancy. Two drives failing is "game over" and the more drives you have (after 2) increases the chance of any two failing. Personally, I'm happy with raid-5 across 6 drives. Then at 7+ drives I move to raid-6, which doesn't fail until 3 drives fail. Raid-6 is like raid-5 in that read speeds are great, but write speeds are a little slower (raid-6 even slower than raid-5). When only one drive has failed, raid-6 performs similar to raid-5 (quite slow, as reading the data from the missing disk requires two reads and a calculation). When two drives have failed, raid-6 can be painfully slow, but still allows you to recover. Raid-6 provides more redundancy than raid-5/0, at the cost of write speeds. The storage requirements are similar. -- Boyd Stephen Smith Jr. ,= ,-_-. =. bss03@volumehost.net ((_/)o o(\_)) ICQ: 514984 YM/AIM: DaTwinkDaddy `-'(. .)`-' http://iguanasuicide.org/ \_/
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