>> One trick I've been using in my ceph clusters is hiding a slow write >> backend behind a fast journal device. The write performance will be of >> the fast (and small) journal device. This only helps on write, but it >> can make a huge difference. >> > > Do you mean an external filesystem journal? What filesystem? ext4/xfs? > I tried that on a physical machine and it worked wonders with both of them, > even though data wasn't journaled and hit the platters - I don't yet > understand how that was possible but the benchmark just flew. >
I just have a raw partition in the journal device (SSD) and point "osd journal" to that block device (something like "osd journal = /dev/vgsde/journal-8"). So no filesystem in the journal device. Then the osd data is in a local HDD using normal XFS filesystem. To help this I do have usually big amounts of RAM (average 6G per OSD), so the buffered writes to the spindle can take it's time to flush. _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
