On Wed, Jul 13, 2016 at 12:14 AM, Di Zhang <zhangdibio@xxxxxxxxx> wrote: > Hi, > > Is there any way to change the metadata pool for a cephfs without losing > any existing data? I know how to clone the metadata pool using rados cppool. > But the filesystem still links to the original metadata pool no matter what > you name it. > > The motivation here is to decrease the pg_num of the metadata pool. I > created this cephfs cluster sometime ago, while I didn't realize that I > shouldn't assign a large pg_num to such a small pool. > > I'm not sure if I can delete the fs and re-create it using the existing > data pool and the cloned metadata pool. It may not be impossible, but it is a wild and crazy untested procedure that I would only do if my system was badly broken and I had no other options. **COMPLETELY UNTESTED AND DANGEROUS** stop all MDS daemons delete your filesystem (but leave the pools) use "rados export" and "rados import" to do a full copy of the metadata to a new pool (*not* cppool, it doesn't copy OMAP data) use "ceph fs new" to create a new filesystem that uses your new metadata pool use "ceph fs reset" to skip the creating phase of the new filesystem start MDS daemons **COMPLETELY UNTESTED AND DANGEROUS** As Christian mentions later in the thread, 512 PGs isn't such a crazy number, so you may well find that your real issue isn't the configuration of your metadata pool. John > Thank you. > > > Zhang Di > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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