Azure disk performance issue

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Azure disk performance issue

Josh Paetzel
I have an issue where a FreeBSD VHD in Azure performs well when reading, and it performs well when writing, but if you throw a mixed read/write workload at it the write performance drops to near zero and latency starts spiking to several hundred milliseconds.

Interestingly enough read performance improves under these conditions.

Looking for some troubleshooting help.

--

Thanks,

Josh Paetzel
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Re: Azure disk performance issue

tech-lists
On Tue, Mar 12, 2019 at 01:01:17PM -0400, Josh Paetzel wrote:
> I have an issue where a FreeBSD VHD in Azure performs well when reading,
> and it performs well when writing, but if you throw a mixed read/write workload
> at it the write performance drops to near zero and latency starts spiking to
> several hundred milliseconds.
>
> Interestingly enough read performance improves under these conditions.
>
> Looking for some troubleshooting help.

I'm very new to freebsd on azure so unfortunately can't be much help at
least initially, but I'd be interested to know what sort of loads you're
putting on it, and what resources the VM has (I mean # of cpu, ram,
size). Any particular software triggering the problem?

I have had to manage php5/mysql on a system where the "disk" was NFS or
something very similar and sometimes it'd thrash under not a particularly
heavy load. But that was years ago on linux. Some software needs attention
or a setting for something like flock or dotlock or similar when
used in a non-baremetal situation.
--
J.
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