On 09/19/2014 10:40 AM, Eric Eastman wrote:
Hi developers,it mentioned in the source code that
OPTION(filestore_zfs_snap,OPT_BOOL, false) // zfsonlinux is still
unstable.
So if we turn on filestore_zfs_snap and neglect journal like btrf,
it will be unstable?As is mentioned on the "zfs on linux community",
It is stable enough to run a ZFS root filesystem on a GNU/Linux
installation for yourworkstation as something to play around with.
It is copy-on-write,supports compression, deduplication, file
atomicity, off-disk caching,(encryption not support), and much more.
So it seems that allfeatures are supported except for
encryption.Thus, I am puzzled that the unstable, you mean, is
ZFS unstableitself. Or it now is already stable on linux, but still
unstable when used as ceph FileStore filesystem.If so,
what will happen if we use it, losing data or frequent crash?
In testing I did last year, there were multiple issues with using ZFS
for my OSD backend, that would lock up the ZFS file systems, and take
the OSD down.
Several of these have been fixed by the ZFS team. See:
https://github.com/zfsonlinux/zfs/issues/1891
https://github.com/zfsonlinux/zfs/issues/1961
https://github.com/zfsonlinux/zfs/issues/2015
The recommendation is to use xattr=sa, but looking at the current open
issues for ZFS, there seems to still be issues with this option. See:
https://github.com/zfsonlinux/zfs/issues/2700
https://github.com/zfsonlinux/zfs/issues/2717
https://github.com/zfsonlinux/zfs/issues/2663
and others
SA xattrs are pretty important from a performance perspective for Ceph
on ZFS based on some testing I did a while back with Brian Behlendorf.
Also per the recent ZFS posting on clusterhq, aio will not be supported
until 0.64 so the following needs to be added to your ceph.conf file
filestore zfs_snap = 1
journal aio = 0
journal dio = 0
My plans are to retest ZFS as an OSD backend once ZFS version 0.64 has
been released.
Please test ZFS with Ceph, and submit bugs, as this is how it will get
stable enough to use in production.
Eric
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