On Mon, 2004-09-13 at 00:41, Russell Coker wrote:
On Mon, 6 Sep 2004 23:35, Adrian 'Dagurashibanipal' von Bidder
<avbidder@fortytwo.ch> wrote:
[...]
Do you have benchmark results to support this assertion? Last time I
tested
the performance of software RAID-1 on Linux I was unable to get
anywhere near
2x disk speed for writing. I did tests by reading two files that
were 1G in
size and the operation took considerably longer than reading a single
1G file
from a non-RAID system. If RAID-1 was delivering twice the read
throughput
then I should be able to read two 1G files concurrently from a RAID-1
in the
same time as would be taken to read a single 1G file from a single
disk.
I think Russel must be checking if the class is awake :-)
That doesn't sound like a fair test; reading two files at once means
the
heads have to bounce around all over the place.
If you are just talking throughput, then reading a 1G file should take
half the time on a RAID-1 that it does on a single disk.
I suspect that reading 2 1G files at once on RAID-1 will be not much
faster than reading 2 1G files on a single disk, because reading two
files at once will probably be seek-bound, not throughput bound. RAID-1
boosts throughput, not latency.