[lug] LVM on SW raid simple tests

[Sean Reifschneider]

On Wed, Jul 25, 2007 at 08:10:10AM -0600, Lee Woodworth wrote:
>No, its not a benchmark. More of a speed limit. If an application
>was getting these kinds of read speeds it would be suspicious.

It really depends on the application.  If it's lots of little reads and
writes all over the disc, yeah, the MB/sec is going to be nowhere near
that.  If it's streaming, that number is about right, except RAID-1
probably should be around twice the read speed of the individual drives,
depending on the array firmware.

For another, slightly less useless benchmark:

   [root at test ~]# grep MemTotal /proc/meminfo
   MemTotal:      4608000 kB
   [root at test ~]# time dd if=/dev/zero of=/tmp/test bs=1000k count=8000
   8000+0 records in
   8000+0 records out
   8192000000 bytes (8.2 GB) copied, 57.9661 s, 141 MB/s

   real    0m58.351s
   user    0m0.024s
   sys     0m33.230s
   [root at test ~]# time dd if=/tmp/test of=/dev/null bs=1000k count=8000
   8000+0 records in
   8000+0 records out
   8192000000 bytes (8.2 GB) copied, 37.6316 s, 218 MB/s

   real    0m37.774s
   user    0m0.016s
   sys     0m3.448s

This is a 8-drive 7200RPM SATA array in RAID-10 with a 3ware card.

Bonnie is a better benchmark, but the default seek settings are way too
small on modern machines, so it requires tweaking quite a bit before you can
get reasonable numbers.  But, it's still only a rough idea of performance.
Benchmarking is *HARD*.

Sean
-- 
 These go to eleven.
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Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
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