Jiri, if you colocate more Journals on 1 SSD (we do...), make sure to understand the following:
- if SSD dies, all OSDs that had their journals on it, are lost... - the more journals you put on single SSD (1 journal being 1 partition), the worse performance, since total SSD performance is not i.e. dedicated/available to only 1 journal, since you are now i.e. colocating 6 journals on 1 SSD...so perromance is 1/6 for each journal... Latenc will go up, bandwith will go down, the more journals you colocate... XFS recommended... I suggest make balance between wanted performance and $$$ for SSDs... best On 29 September 2015 at 13:32, Jiri Kanicky <[email protected]> wrote: > Hi Lionel. > > Thank you for your reply. In this case I am considering to create separate > partitions for each disk on the SSD drive. Would be good to know what is > the performance difference, because creating partitions is kind of waste of > space. > > One more question, is it a good idea to move journal for 3 OSDs to a > single SSD considering if SSD fails the whole node with 3 HDDs will be > down? Thinking of it, leaving journal on each OSD might be safer, because > journal on one disk does not affect other disks (OSDs). Or do you think > that having the journal on SSD is better trade off? > > Thank you > Jiri > > > On 29/09/2015 21:10, Lionel Bouton wrote: > >> Le 29/09/2015 07:29, Jiri Kanicky a écrit : >> >>> Hi, >>> >>> Is it possible to create journal in directory as explained here: >>> >>> http://wiki.skytech.dk/index.php/Ceph_-_howto,_rbd,_lvm,_cluster#Add.2Fmove_journal_in_running_cluster >>> >> Yes, the general idea (stop, flush, move, update ceph.conf, mkjournal, >> start) is valid for moving your journal wherever you want. >> That said it probably won't perform as well on a filesystem (LVM as >> lower overhead than a filesystem). >> >> 1. Create BTRFS over /dev/sda6 (assuming this is SSD partition alocate >>> for journal) and mount it to /srv/ceph/journal >>> >> BTRFS is probably the worst idea for hosting journals. If you must use >> BTRFS, you'll have to make sure that the journals are created NoCoW >> before the first byte is ever written to them. >> >> 2. Add OSD: ceph-deploy osd create --fs-type btrfs >>> ceph1:sdb:/srv/ceph/journal/osd$id/journal >>> >> I've no experience with ceph-deploy... >> >> Best regards, >> >> Lionel >> >> > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- Andrija Panić
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