On 08/22/2014 05:23 PM, Jens Axboe wrote:
On 2014-08-18 19:42, Mark Nelson wrote:
Hi Guys,
I'm using the librbd engine and trying to determine what exactly happens
when multiple --name parameters are passed. Primarily, I'm wondering if
each fio process ends up writing to the same blocks on the rbd volume
during sequential writes. Looking at the code, I see a note that we
pretend to deal with files even if the engine doesn't understand the
concept of files:
https://github.com/axboe/fio/blob/master/engines/rbd.c#L405
https://github.com/axboe/fio/blob/master/filesetup.c#L1239
I'm not seeing anything (might be missing it) in the rbd engine or there
that would partition the volume based on the process though. Am I
missing anything?
The same thing will happen as if you ran two instances of fio with the
same options. For rbd, each job will create/connect/open and rbd
instance. For each of these, you can set the rbd pool and clientname.
Thanks Jens. What I'd like to be able to do is start multiple fio
processes but have each one only write to a non-overlapping portion of
the block device. Preferably I wouldn't have to manually figure out the
ranges myself. Any way to do something like that?
For now if we are interested in 4MB IOs to RBD we can just do 4MB random
as that more or less translates into the same thing behind the scenes in
Ceph anyway.
Mark
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