[DRBD-user] Extremely high latency problem

Bret Mette bret.mette at dbihosting.com
Fri Jun 6 01:00:20 CEST 2014

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hey Phillip,

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!).


Thank you so much, I couldn't be happier.


- Bret


On Thu, Jun 5, 2014 at 3:34 AM, Philipp Marek <philipp.marek at linbit.com>
wrote:

> Hi Bret,
>
> > Intel(R) Xeon(R) CPU E3-1230 V2 @ 3.30GH
> > CentoS 6.5 - 2.6.32-431.17.1.el6.x86_64
> > drbd version: 8.3.16 (api:88/proto:86-97)
> please use 8.4.4 (or .5).
> Eg because of http://blogs.linbit.com/p/469/843-random-writes-faster/
>
>
> > dd if=/dev/zero of=./testbin  bs=512 count=1000 oflag=direct
> > 512000 bytes (512 kB) copied, 32.3254 s, 15.8 kB/s
> This means ~32msec per write.
>
> But: you're writing into a _filesystem_, not directly onto the DRBD
> resource.
> And that means quite some write amplification - each 512 byte write
> _might_ result (depending on the filesystem) in _multiple_ write-
> requests, each with a separate barrier ...
>
>
> Please try writing into a DRBD device, without any filesystem inbetween;
> and using 4kB blocks might help to avoid read/modify/write cycles, too.
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20140605/bf39e3bb/attachment.htm>


More information about the drbd-user mailing list