Le 10/01/2014 17:16, Bradley Kite a écrit :
This might explain why the performance is not so good - on each connection it can only do 1 transaction at a time:

1) Submit write
2) wait...
3) Receive ACK

Then repeat...

But if the OSD protocol supports multiple transactions it could do something like this:

1) Submit 1
2) Submit 2
3) Submit 3
4) Recv ACK 1
5) Submit 4
6) Recv ACK 2
What you are describing here are sync and async writes, from what I understand those behaviours are defined by initial write calls flags (posix O_SYNC or O_ASYNC), and ideally have to be honoured all the way to the final storage back-end (the drives) to ensure data consistency (if something goes wrong). For exemple : fio => iSCSI => CEPH => drives

What options did you pass to your benchmark tool ?

--
Cédric

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