Re: Filestore merge and split

[Anand Bhat <anand.bhat@xxxxxxxxx>]

Merge happens either due to movement of objects due to CRUSH recalculation (when cluster grows or shrinks due to various reasons) or deletion of objects.

Split happens when portions of objects/volumes get populated that were previously sparse. Each RADOS object by default is 4MB chunk and volumes comprise of these objects There is no RADOS object created when there is no write on that region. When write spans sparse portions of the volume, new RADOS objects are created under directory that maps the PG to which the object belongs.

Regards,

Anand

On Mon, Jul 11, 2016 at 5:38 PM, Nick Fisk <nick@xxxxxxxxxx> wrote:

I believe splitting will happen on writes, merging I think only happens on deletions.

 

From: Paul Renner [mailto:rennerp78@xxxxxxxxx]
Sent: 10 July 2016 19:40
To: nick@xxxxxxxxxx
Cc: ceph-users@xxxxxxxxxxxxxx
Subject: Re: Filestore merge and split

 

Thanks...

Do you know when splitting or merging will happen? Is it enough that a directory is read, eg. through scrub? If possible I would like to initiate the process

Regards

Paul

 

On Sun, Jul 10, 2016 at 10:47 AM, Nick Fisk <nick@xxxxxxxxxx> wrote:

You need to set the option in the ceph.conf and restart the OSD I think. But it will only take effect when splitting or merging in the future, it won't adjust the current folder layout.

> -----Original Message-----
> From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Paul Renner
> Sent: 09 July 2016 22:18
> To: ceph-users@xxxxxxxxxxxxxx
> Subject: Filestore merge and split
>
> Hello cephers
> we have many (millions,  small objects in our RadosGW system and are getting not very good write performance, 100-200 PUTs /sec.
>
> I have read on the mailinglist that one possible tuning option would be to increase the max. number of files per directory on OSDs with
> eg.
>
> filestore merge threshold = 40
> filestore split multiple = 8
> Now my question is, do we need to rebuild the OSDs to make this effective? Or is it a runtime setting?
> I'm asking because when setting this with injectargs I get the message "unchangeable" back.
> Thanks for any insight.

 

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