Re: poor write performance

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On 04/19/2013 06:09 AM, James Harper wrote:
I just tried a 3.8 series kernel and can now get 25mbytes/second using dd with a 4mb block size, instead of the 700kbytes/second I was getting with the debian 3.2 kernel.

That's.... unexpected. Was this the kernel on the client, the OSDs, or both?


I'm still getting 120kbytes/second with a dd 4kb block size though... is that expected?

that's still quite a bit lower than I'd expect as well. What were your fs mount options on the OSDs? Can you try some rados bench read/write tests on your pool? Something like:

rados -p <pool> -b 4096 bench 300 write --no-cleanup -t 64
rados -p <pool> -b 4096 bench 300 seq -t 64

with 2 drives and 2x replication I wouldn't expect much without RBD cache, but 120kb/s is rather excessively bad. :)


James


Mark
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