[Consult-list] Re: [dm-devel] dm-multipath has great throughput but we'd like more!

[Nicholas C. Strugnell]

On Thu, 2006-05-18 at 10:04 +0200, Nicholas C. Strugnell wrote: 
> On Thu, 2006-05-18 at 08:44 +0100, Bob Gautier wrote:
> > On Thu, 2006-05-18 at 02:25 -0500, Jonathan E Brassow wrote:
> > > The system bus isn't a limiting factor is it?  64-bit PCI-X will get 
> > > 8.5 GB/s (plenty), but 32-bit PCI 33MHz got 133MB/s.
> > > 
> > > Can your disks sustain that much bandwidth? 10 striped drives might get 
> > > better than 200MB/s if done right, I suppose.
> > > 
> 

> It might make sense to test raw writes to a device with dd and see if
> that gets comparable performance figures - I'll just try that myself
> actually.

write throughput to EVA 8000 (8GB write cache), host DL380 with 2x2Gb/s
HBAs, 2GB RAM

testing 4GB files:

on filesystems: bonnie++ -d /mnt/tmp -s 4g -f -n 0 -u root

ext3: 129MB/s sd=0.43

ext2: 202MB/s sd=21.34

on raw: 216MB/s sd=3.93  (dd if=/dev/zero of=/dev/mpath/3600508b4001048ba0000b00001400000 bs=4k count=1048576)


NB I did not have exclusive access to the SAN or this particular storage
array - this is a big corp. SAN network under quite heavy load and disk
array under moderate load - not even sure if I had exclusive access to
the disks. All values averaged over 20 runs. 

The very low deviation of write speed on ext3 vs. exr2 or raw is
interesting - not sure if it means anything.

In any case, we don't manage to get very close to the theoretical
throughput of the 2 HBAs, 512MB/s

Nick



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