<div dir="ltr">Hey Phillip,<div><br></div><div>I upgraded to 8.4.4 and it totally resolved my issue. My targets went from 0.5 - 1.1M/sec writes to 30M/sec writes on random writes and 7M/sec (with caching turned on) to 85M/sec (with no caching!).</div>
<div><br></div><div><br></div><div>Thank you so much, I couldn't be happier.</div><div><br></div><div><br></div><div>- Bret</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Jun 5, 2014 at 3:34 AM, Philipp Marek <span dir="ltr"><<a href="mailto:philipp.marek@linbit.com" target="_blank">philipp.marek@linbit.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Bret,<br>
<div class=""><br>
> Intel(R) Xeon(R) CPU E3-1230 V2 @ 3.30GH<br>
> CentoS 6.5 - 2.6.32-431.17.1.el6.x86_64<br>
> drbd version: 8.3.16 (api:88/proto:86-97)<br>
</div>please use 8.4.4 (or .5).<br>
Eg because of <a href="http://blogs.linbit.com/p/469/843-random-writes-faster/" target="_blank">http://blogs.linbit.com/p/469/843-random-writes-faster/</a><br>
<div class=""><br>
<br>
> dd if=/dev/zero of=./testbin bs=512 count=1000 oflag=direct<br>
> 512000 bytes (512 kB) copied, 32.3254 s, 15.8 kB/s<br>
</div>This means ~32msec per write.<br>
<br>
But: you're writing into a _filesystem_, not directly onto the DRBD<br>
resource.<br>
And that means quite some write amplification - each 512 byte write<br>
_might_ result (depending on the filesystem) in _multiple_ write-<br>
requests, each with a separate barrier ...<br>
<br>
<br>
Please try writing into a DRBD device, without any filesystem inbetween;<br>
and using 4kB blocks might help to avoid read/modify/write cycles, too.<br>
<br>
<br>
</blockquote></div><br></div>