On Wed, 18 Aug 1999, James Manning wrote:
> > I missed the start of this thread, so I don't know what RAID level you're
> > using. I did some RAID-0 tests with the new Linux RAID code back in March
> > on a dual 450Mhz Xeon box. Throughput on a single LVD bus appears to peak
> > at about 55MBs - you can get 90% of this with four 7,200RPM Baracudas.
> > With two LVD busses, write performance peaks at just over 70MBs
> > (diminishing returns after six disks)
>
> Could you describe the set-up? When I switched to s/w raid0 over
> h/w raid0 just for testing, my block write rate in bonnie only went
> up to 43 MB/sec. All the best performance has come with the smallest
> chunk-sizes that make sense (4k), where my improvement was significant
> over 64k chunk-sizes.
RAID0-8Disks-2Bus-MDChunk32_Stride256_QDepth10
Seeker 1...Seeker 2...Seeker 3...start 'em...done...done...done...
-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
1000 6538 98.9 72882 76.6 24213 54.7 5963 98.9 78587 76.3 387.2 5.0
I found the SCSI queue depth, RAID chunk size and stride size made
only small differences in bonie results. The largest improvement in
performance comes from using a 4K filesystem block size.
Check out:
http://www-hpcc.astro.washington.edu/reschke/Linux_MD_Benchmarks/
I've included the bonnie output and a couple of graphs - one showing
throughput as a function of the # of disks and SCSI busses, and
another showing Bonnie's sensitivity to the the test-size/RAM-size
ratio.
- C
