On 06/03/14 09:36, Gandalf Corvotempesta wrote: > Hi to all. > Some question about ansible repo. > > 1. is possible to specify multiple journal devices for each OSD node? > We have OSD with 12 spinning disks and 2 SSD as journal. We would like > to use SSD1 for OSD1 to 6 and SSD2 for OSD 7 to 12. Is this possible ? One option I'm currently testing is whereby the two SSDs in a node are stitched together into a Linux software-RAID striped array, and then allocate the journal partitions on the resulting /dev/md device. This is currently working well, save that the default udev rules for mapping OSDs explicitly skip over md journal devices; removing the "|md*" term in the relevant ruleset resolves this problem. (This is in my workqueue to report as a bug.) This causes the IO load to be nicely balanced across the two SSDs, removing any hot spots, at the cost of enlarging the failure domain of the loss of an SSD from half a node to a full node. One potential optimization which I haven't yet investigated is to see whether moving the XFS filesystem journal, in addition to the OSd journal, might result in an improvement in performance — in particular on nodes which are equipped with slower 'green' drives. This is not something that ceph-deploy currently makes easy; if, as I expect, I find myself re-implementing the ceph-deploy functions in terms of Ansible rules — perhaps using LVM rather than GPT partitions? — I may then be able to try some experiments. Kind regards, David -- David McBride <dwm37@xxxxxxxxx> Unix Specialist, University Computing Service -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
