On Thu, Jun 28, 2007 at 10:30:23 +0200, Mogens Kjaer mk@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.