[ale] RAID, IDE and/or Linux

Chris Ricker kaboom at gatech.edu
Sat Feb 16 15:21:22 EST 2002


On Sat, 16 Feb 2002, Jeff Hubbs wrote:

> Chris Ricker wrote:
> 
> >On Sat, 16 Feb 2002, Jeff Hubbs wrote:
> >
> >>The downside to RAID 1 here is the 1:2 effective/actual capacity ratio, 
> >>i.e., takes 40GB to make 20.  If he goes RAID 5 instead and the 
> >>three-drive medium, he gets a ~2:3 ratio - takes 60GB to get 40.  
> >>
> >
> >But loses instantaneous fallover....
> >
> 
> Since when??

Since always.  By definition, with RAID-5, you don't have a live copy of
data like with RAID-1 -- you have dispersed parity bits from which data can
be slowly reconstructed.  Even when you have hot spare(s) (and I hope if
you're using RAID-5 that you do), you still have to wait for the new drive
to be rebuilt from the parity on the remaining disks.  Until the new drive
finishes rebuilding, you run in a degraded mode where data is reconstructed,
not live.

later,
chris


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