FWIW, we run into this same issue, and cannot get a good enough SSD: spinning ratio, and decided on simply running the journals on each (spinning) drive, for hosts that have 24 slots. The problem gets even worse when we're talking about some of the newer boxes.
Warren Warren On Wed, Sep 18, 2013 at 1:56 PM, Mike Dawson <mike.daw...@cloudapt.com>wrote: > Joseph, > > With properly architected failure domains and replication in a Ceph > cluster, RAID1 has diminishing returns. > > A well-designed CRUSH map should allow for failures at any level of your > hierarchy (OSDs, hosts, racks, rows, etc) while protecting the data with a > configurable number of copies. > > That being said, losing a series of six OSDs is certainly a hassle and > journals on a RAID1 set could help prevent that senerio. > > But where do you stop? 3 monitors, 5, 7? RAID1 for OSDs, too? 3x > replication, 4x, 10x? I suppose each operator gets to decide how far to > chase the diminishing returns. > > > Thanks, > > Mike Dawson > Co-Founder & Director of Cloud Architecture > Cloudapt LLC > > On 9/18/2013 1:27 PM, Gruher, Joseph R wrote: > >> >> >> -----Original Message----- >>> From: >>> ceph-users-boun...@lists.ceph.**com<ceph-users-boun...@lists.ceph.com>[mailto: >>> ceph-users- >>> boun...@lists.ceph.com] On Behalf Of Mike Dawson >>> >>> you need to understand losing an SSD will cause >>> the loss of ALL of the OSDs which had their journal on the failed SSD. >>> >>> First, you probably don't want RAID1 for the journal SSDs. It isn't >>> particularly >>> needed for resiliency and certainly isn't beneficial from a throughput >>> perspective. >>> >> >> Sorry, can you clarify this further for me? If losing the SSD would >> cause losing all the OSDs journaling on it why would you not want to RAID >> it? >> >> ______________________________**_________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/**listinfo.cgi/ceph-users-ceph.**com<http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com> >
_______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
