[Gluster-users] glusterfsd Ubuntu 18.04 high iowait issues

Amar Tumballi Suryanarayan atumball at redhat.com
Thu Feb 21 05:18:44 UTC 2019

If you have both systems to get some idea, can you get the `gluster profile
info' output? That helps a bit to understand the issue.

On Thu, Feb 21, 2019 at 8:20 AM Kartik Subbarao <subbarao at computer.org>

> We're running gluster on two hypervisors running Ubuntu. When we
> upgraded from Ubuntu 14.04 to 18.04, it upgraded gluster from 3.4.2 to
> 3.13.2. As soon as we upgraded and since then, we've been seeing
> substantially higher iowait on the system, as measured by top and iotop,
> and iotop indicates that glusterfsd is the culprit. For some reason,
> glusterfsd is doing more disk reads and/or those reads are being held up
> up at a greater rate. The guest VMs are also seeing more iowait -- their
> images are hosted on the gluster volume. This is causing inconsistent
> responsiveness from the services hosted on the VMs.
> I'm looking for any recommendations on how to troubleshoot and/or
> resolve this problem. We have other sites that are still running 14.04,
> so I can compare/contrast any configuration parameters and performance.
> The block scheduler on 14.04 was set to deadline and 18.04 was set to
> cfq. But changing the 18.04 scheduler to deadline didn't make any
> difference.
> I was wondering whether glusterfsd on 18.04 isn't caching as much as it
> should. We tried increasing performance.cache-size substantially but
> that didn't make any difference.
> Another option we're considering but haven't tried yet is upgrading to
> gluster 5.3 by back-porting the package from Ubuntu 19.04 to 18.04. Does
> anyone think this might help?
> Is there any particular debug logging we could set up or other commands
> we could run to troubleshoot this better? Any thoughts, suggestions,
> ideas would be greatly appreciated.
> Thanks,
>      -Kartik
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Amar Tumballi (amarts)
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