Re: osd bench with or without a separate WAL device deployed

["rainning" <tweetypie@xxxxxx>]

one more thing it seems that WAL does have more impact on small write. 



---Original---
From: "Zhenshi Zhou"<deaderzzs@xxxxxxxxx&gt;
Date: Wed, Jul 15, 2020 18:39 PM
To: "rainning"<tweetypie@xxxxxx&gt;;
Cc: "ceph-users"<ceph-users@xxxxxxx&gt;;
Subject:  Re: osd bench with or without a separate WAL device deployed


I deployed the cluster either with separate db/wal or put db/wal/data
together. Never tried to have only a seperate db.
AFAIK wal does have an effect on writing but I'm not sure if it could be
two times of the bench value. Hardware and
network environment are also important factors.

rainning <tweetypie@xxxxxx&gt; 于2020年7月15日周三 下午4:35写道：

&gt; Hi all,
&gt;
&gt;
&gt; I am wondering if there is any performance comparison done on osd bench
&gt; with and without a separate WAL device deployed given that there is always
&gt; a separate db device deployed on SSD in both cases.
&gt;
&gt;
&gt; The reason I am asking this question is that we have two clusters and osds
&gt; in one have separate db and WAL device deployed on SSD but osds in another
&gt; only have a separate db device deployed. And we found 4KB osd bench (i.e.
&gt; ceph tell osd.X bench 12288000 4096) for the ones having a separate WAL
&gt; device was two times of the ones without a separate WAL device. Is the
&gt; performance difference caused by the separate WAL device?
&gt;
&gt;
&gt; Thanks,
&gt; Ning
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