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List:       ceph-users
Subject:    [ceph-users] Re: High ceph_osd_commit_latency_ms on Toshiba MG07ACA14TE HDDs
From:       Benoît_Knecht <bknecht () protonmail ! ch>
Date:       2020-06-24 13:45:25
Message-ID: -qP5YFh2VSx6hrjHC1kps3_QsreoXCmnKjHQHCOi00BlPbL_xtHe3sHqUyEXI59vqsMGJ4rEqEz0cqu0yJC0OX1IQa22OgKNSwAVNhL5FD8= () protonmail ! ch
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Hi Igor,

Igor Fedotov wrote:
> for the sake of completeness one more experiment please if possible:
>
> turn off write cache for HGST drives and measure commit latency once again.

I just did the same experiment with HGST drives, and disabling the write cache
on those drives brought the latency down from about 7.5ms to about 4ms.

So it seems disabling the write cache across the board would be advisable in
our case. Is it recommended in general, or specifically when the DB+WAL is on
the same hard drive?

Stefan, Mark, are you disabling the write cache on your HDDs by default?

Cheers,

--
Ben
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