On Fri, Sep 14, 2012 at 8:51 AM, Travis Rhoden <[email protected]> wrote: > On a running Ceph cluster using XFS for the OSD's, is it safe to > defrag the OSD devices while the system is live? > > I did a quick check of one device: > > xfs_db -c frag -r /dev/sdd > actual 637596, ideal 144935, fragmentation factor 77.27%
If it's safe to defrag xfs while it's mounted in general, it's safe to do it when an OSD is running. Xfs either keeps its promises as a filesystem, or doesn't. How that affects performance is another question.. > While I'm talking about XFS... I know that RBD's use a default object > size of 4MB. I've stuck with that so far.. Would it be beneficial to > mount XFS with -o allocsize=4M ? What is the object size that gets > used for non-RBD cases -- i.e. just dumping objects into data pool? Don't know about -o allocsize -- benchmark it! Objects are the size they are; Ceph does not dictate any size. RBD and CephFS both stripe a thing (image/file) over multiple objects, at a constant size; you already know that, RBD defaults to 4MB. Other users of RADOS create objects of any size they please, and an OSD stores those as files in the underlying filesystem. -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
