On Fri, Sep 25, 2015 at 5:53 PM, Межов Игорь Александрович
<megov@xxxxxxxxxx> wrote:
> Hi!
>
> Thanks!
>
> I have some suggestions for the 1st method:
>
>>You could get the name prefix for each RBD from rbd info,
> Yes, I did it already at the steps 1 and 2. I forgot to mention, that I grab
> rbd frefix from 'rbd info' command
>
>
>>then list all objects (run find on the osds?) and then you just need to
>> grep the OSDs for each prefix.
> So, you advise to run find over ssh for all OSD hosts to traverse OSDs
> filesystems and find files (objects),
> named with rbd prefix? Am I right? If so, I have two thoughts: (1) it may be
> not so fast also, because
> even limiting find with rbd prefix and pool index, it have to recursively go
> through whole OSD filesytem
> hierarchy. And (2) - find will put an additional load to OSD drives.
>
>
> The second method is more attractive and I will try it soon. As we have an
> object name,
> and can get a crushmap in some usable form to look by ourself, or indirectly
> through a
> library/api call - finding the chain of object-to-PG-to-OSDs is a local
> computational
> task, and it can be done without remote calls (accessing OSD hosts, finding,
> etc).
>
> Also, the slow looping through 'ceph osd map <pool> <object>' could be
> explained:
> for every object we have to spawn process, connecting cluster (with auth),
> receiving
> maps to client, calculating placement, and ... finally throw it all away
> when process
> exits. I think this overhead is a main reason of slowness.
Internally there is a way to list objects within a specific PG
(actually more than one way IIRC), but I don't think anything like that
is exposed in a CLI (it might be exposed in librados though). Grabbing
an osdmap and iterating with osdmaptool --test-map-object over
rbd_data.<prefix>.* is probably the fastest way for you to get what you
want.
Thanks,
Ilya
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