[F7] Most reliable RAID level

[Bruno Wolff III]

On Thu, Jun 28, 2007 at 10:30:23 +0200,
  Mogens Kjaer <mk at crc.dk> wrote:
> Chris Tyler wrote:
> ...
> > If the disks are on separate controllers, you can
> >read and write them in parallel, yielding good performance (1x write, Nx
> >read).
> 
> Why is it that I don't see this for a RAID-1 system?
> 
> 2xSATA 160G disks:
> 
> RAID 1:
> 
> Write 20G file: 52.5 MB/sec
> Read 20G file: 63.6 MB/sec
> 
> RAID 0:
> 
> Write 20G file: 107 MB/sec
> Read 20G file: 105 MB/sec
> 
> I would have expected the number 63.6 MB/sec to be
> higher.

How are you testing this? If you are reading sequential blocks you aren't
going to get much in the way of savings from two disks. If you have two
simultaneous sequential reads going from different locations, then I would
expect big savings since many seeks could be avoided.