Re: Raid ?

On Fri, 6 Jan 2006 14:34:21 +0000 (UTC), "Rob Nicholson"
<rob.nicholson@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

>> Yeah but RAID-0 with 2 disks is twice as likely to fail :-)
>
>Hmm, not sure I agree with your math :-) Let's say you've got two 120MB
>RAID-0 drivers giving you 240MB total. Sure, one half fails and you're
>screwed. So if you weren't going to use RAID for speed, then you'd probably
>get one bigger hard disk. Therefore, you've still got the same chance of it
>failing.

If each drive has a 1-in-100,000 chance of failing every hour, then
every hour one (250gig) drive has a 1-in-100,000 chance of dying.

Two (120gig) drives in a raid0 array, each at 1-in-100,000 chance per
hour --> 2 in 100,000 chance of _one_ of them dying per hour.

If you push it out further to make it more obvious, a raid of 100,000
drives would have one die per hour, on average.

>As just to tempt fate, my IDE RAID array did fail yesterday

Bad luck. I've had to RMA a couple of 250gb WD SATAs (the JD models)
at work in the last year, never any other WD drives. Hmm.

>all I've lost is a few days of stuff, mainly email. And because lovely GMAIL
>keeps it all your old email, it's was easy to get that back.

Splendid!

Cheers - Jaimie
--
"Every Little Thing She Does Is Sufficiently Advanced Technology"
.

Relevant Pages

  • Re: RAID support different size hard drives
    ... If only one fails and you replace it before a second one fails, yes, you are ... SuperGumby [SBS MVP] wrote: ... The drives should not only be the same size but the same geometry ... supporting configuring different size hard drives. ...
    (microsoft.public.windows.server.sbs)
  • Re: What is the point of RAID?
    ... "adding more drives only increases the chances of the whole array to ... that's exactly what I mean by least chance of failure. ... RAID-5 always grows in storage not redundancy, and fails as soon as any two ...
    (Debian-User)
  • Re: Old Possums book of practical hosts.
    ... 30% chance of not working on power up. ... stupid design of centronics-50 connector and sub-cables etc. ... *might* be low-cost caddies avasilable for those drives that actually ...
    (alt.sysadmin.recovery)
  • Re: Sun Ultra 40 M2 hard drive sleds
    ... Hmm ... ... primary CPU has directly connected RAM while the secondary CPU doesn't ... I've recently seen 146 GB FC-AL drives go for less than ...
    (comp.sys.sun.hardware)
  • Re: [9fans] Recovering a venti from disk failure
    ... erik quanstrom wrote: ... Assuming a RAID is built from similar disks, when one fails ... the probability of the other drives failing has not ... No RAID then of course. ...
    (comp.os.plan9)