On Thu, 1 Dec 2016 18:06:38 -0600 Reed Dier wrote:
> Apologies if this has been asked dozens of times before, but most answers are
> from pre-Jewel days, and want to double check that the methodology still
> holds.
>
It does.
> Currently have 16 OSD’s across 8 machines with on-disk journals, created
> using ceph-deploy.
>
> These machines have NVMe storage (Intel P3600 series) for the system volume,
> and am thinking about carving out a partition for SSD journals for the OSD’s.
> The drives don’t make tons of use of the local storage, so should have plenty
> of io overhead to support the OSD journaling, as well as the P3600 should
> have the endurance to handle the added write wear.
>
Slight disconnect there, money for a NVMe (which size?) and on disk
journals? ^_-
> From what I’ve read, you need a partition per OSD journal, so with the
> probability of a third (and final) OSD being added to each node, I should
> create 3 partitions, each ~8GB in size (is this a good value? 8TB OSD’s, is
> the journal size based on size of data or number of objects, or something
> else?).
>
Journal size is unrelated to the OSD per se, with default parameters and
HDDs for OSDs a size of 10GB would be more than adequate, the default of
5GB would do as well.
> So:
> {create partitions}
> set noout
> service ceph stop osd.$i
> ceph-osd -i osd.$i —flush-journal
> rm -f rm -f /var/lib/ceph/osd/<osd-id>/journal
Typo and there should be no need for -f. ^_^
> ln -s /var/lib/ceph/osd/<osd-id>/journal /dev/<ssd-partition-for-journal>
Even though in your case with a single(?) NVMe there is little chance for
confusion, ALWAYS reference to devices by their UUID or similar, I prefer
the ID:
---
lrwxrwxrwx 1 root root 44 May 21 2015 journal ->
/dev/disk/by-id/wwn-0x55cd2e404b73d570-part4
---
> ceph-osd -i osd.$i -mkjournal
> service ceph start osd.$i
> ceph osd unset noout
>
> Does this logic appear to hold up?
>
Yup.
Christian
> Appreciate the help.
>
> Thanks,
>
> Reed
--
Christian Balzer Network/Systems Engineer
[email protected] Global OnLine Japan/Rakuten Communications
http://www.gol.com/
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