Interesting results

["Jim Schutt" <jaschut@sandia.gov>]

Hi,

Lots of trouble reports go by on the list - I thought
it would be useful to report a success.

Using a patch (https://lkml.org/lkml/2012/6/28/446)
on top of 2.5-rc4 for my OSD servers, the same kernel
for my Linux clients, and a recent master branch
tip (git://github.com/ceph/ceph commit 4142ac44b3f),
I was able to sustain streaming writes from 166 linux
clients for 2 hours:

On 166 clients:
   dd conv=fdatasync if=/dev/zero of=/mnt/ceph/stripe-4M/1/zero0.`hostname -s` bs=4k count=65536k

Elapsed time:   7274.55 seconds
Total data:     45629732.553 MB (43515904 MiB)
Aggregate rate: 6272.516 MB/s

That kernel patch was critical; without it this test
runs into trouble after a few minutes because the
kernel runs into trouble looking for pages to merge
during page compaction.  Also critical were the ceph
tunings I mentioned here:
   http://www.spinics.net/lists/ceph-devel/msg07128.html

-- Jim