Re: how to debug slow rbd block device

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Am 22.05.2012 16:52, schrieb Andrey Korolyov:
Hi,

I`ve run in almost same problem about two months ago, and there is a
couple of corner cases: near-default tcp parameters, small journal
size, disks that are not backed by controller with NVRAM cache and
high load on osd` cpu caused by side processes. Finally, I have able
to achieve 115Mb/s for large linear writes on raw rbd block inside VM
with journal on tmpfs and osds on RAID0 built on top of three sata
disks.

which tcp parameters could you recommand? The journal size is 1Gb on tmpfs right now. Instead of 3 sata disks i'm using one intel ssd. the CPU is loaded by 10% on each osd max. A "ceph osd tell X bench" shows me 260MB/s write on each OSD (intel ssd).

Greets
Stefan
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