Moving Journal to SSD

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Hi Dane,

If you deployed with ceph-deploy, you will see that the journal is just a symlink.
Take a look at /var/lib/ceph/osd/<osd-id>/journal
The link should point to the first partition of your hard drive disk, so no filesystem for the journal, just a block device.

Roughly you should try:

create N partition on your SSD for your N OSDs
ceph osd set noout
sudo service ceph stop osd.$ID
ceph-osd -i osd.$ID --flush-journal
rm -f /var/lib/ceph/osd/<osd-id>/journal
ln -s  /var/lib/ceph/osd/<osd-id>/journal /dev/<ssd-partition-for-your-journal>
ceph-osd -i osd.$ID ?mkjournal
sudo service ceph start osd.$ID
ceph osd unset noout

This should work.

Cheers.

On 11 Aug 2014, at 18:36, Dane Elwell <dane.elwell at gmail.com> wrote:

> Hi list,
> 
> Our current setup has OSDs with their journal sharing the same disk as
> the data, and we've reached the point we're outgrowing this setup.
> We're currently vacating disks in order to replace them with SSDs and
> recreate the OSD journals on the SSDs in a 5:1 ratio of spinners to
> SSDs.
> 
> I've read in a few places that it's possible to move the OSD journals
> without losing data on the OSDs, which is great, however none of the
> stuff I've read seems to cover our case.
> 
> We installed Ceph using ceph-deploy, putting the journals on the same
> disks. ceph-deploy doesn't populate a ceph.conf file fully, so we
> don't have e.g. individual OSD entries in there.
> 
> If I'm understanding this correctly, the Ceph disks are automounted by
> udev rules from /lib/udev/rules.d/95-ceph-osd.rules, and this mounts
> the OSD disk (partition 1) then mounts the journal under /journal
> (partition 2 of the same disk).
> 
> That's all well and good, but as I now want to move the journal, how
> do I go about telling Ceph where the new journals are located so they
> can be mounted in the right location? Do I need to populate ceph.conf
> with individual entries for all OSDs or is there a way I can make udev
> do all the heavy lifting?
> 
> Regards
> 
> Dane
> _______________________________________________
> ceph-users mailing list
> ceph-users at lists.ceph.com
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com


Cheers.
???? 
S?bastien Han 
Cloud Architect 

"Always give 100%. Unless you're giving blood."

Phone: +33 (0)1 49 70 99 72 
Mail: sebastien.han at enovance.com 
Address : 11 bis, rue Roqu?pine - 75008 Paris
Web : www.enovance.com - Twitter : @enovance 

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