Re: [ceph-users] Cache pool tiering SSD journal
No, if you used cache tiering, It is no need to use ssd journal again. From: Florent MONTHEL Date: 2015-01-17 23:43 To: ceph-users Subject: [ceph-users] Cache pool tiering SSD journal Hi list, With cache pool tiering (in write back mode) enhancement, should I keep to use SSD journal on SSD ? Can we have 1 big SSD pool for caching for all low cost storage pools ? Thanks Florent Monthel ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] Cache pool tiering SSD journal
On 01/17/2015 08:17 PM, lidc...@redhat.com wrote: No, if you used cache tiering, It is no need to use ssd journal again. The cache tiering and SSD journals serve a somewhat different purpose. In Ceph, all of the data for every single write is written to both the journal and to the data storage device. SSD journals allow you to avoid additional coalesced O_DSYNC sequential writes to the data disk. In some situations this can provide up to a 2X write performance improvement on the base tier OSDs. Cache pool tiering may also provide some coalescing of writes to the base pool, but doesn't help you avoid the additional journal write penalty on the base tier OSDs. It does however provide the benefit of allowing you to read hot data from the cache tier and potentially avoid read/write head seek contention if you have spinning disks on the base tier. Mark ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] Cache pool tiering SSD journal
On Sun, 18 Jan 2015 10:17:50 AM lidc...@redhat.com wrote: No, if you used cache tiering, It is no need to use ssd journal again. Really? writes are as fast as with ssd journals? ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
[ceph-users] Cache pool tiering SSD journal
Hi list, With cache pool tiering (in write back mode) enhancement, should I keep to use SSD journal on SSD ? Can we have 1 big SSD pool for caching for all low cost storage pools ? Thanks Florent Monthel ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
