Re: [squid-users] squid with linux or freeBSD?

On Thu, May 01, 2003 at 12:30:00PM +0800, fooler wrote:
>
>
> > Doesn't performance actually *increase* if you lose a disk? Sure you're
> > "degraded" as far as redundancy goes but performance-wise you win because
> some
> > percentage of reads (and writes?) no longer involves the parity
> calculation
> > (it's on the missing disk) and so occur faster.
>
> true and those parity informations available on the available disks turn
> into data block and not parity block anymore thus your raid 5 turns into
> raid 0 on that situation :->
>

No. Your performance degrades. You get slower and you risk losing
your data if another disk dies. You get a lower read performance
because the data must be reconstructed from the information on the
disks instead of just reading the stripe and plucking the data out. I
would _guess_ that writing would be the same since the parity is
calculated anyway. Raid 5 does not degrade to raid 0 ... ever, the
data striping is not done like that. You could _almost_ say that
about RAID 3 but hardly anyone supports doing RAID 3 due to the
drawbacks of having the parity stored on one disk.

You guys really need to google for some raid basics :-(

-- 
Brett Lymn