Not a bloody chance... WriteBack is the only thing that gives both acceptable performance characteristics and data guarantees. (The NFS file server running ZFS is running in sync=disabled mode, but it also has dual power supplies connected to dual UPSes, and I'm willing to take the chance of a complete system failure.) -Adam
> -----Original Message----- > From: pve-user [mailto:[email protected]] On > Behalf Of Emmanuel Kasper > Sent: October 11, 2016 05:26 > To: PVE User List <[email protected]> > Subject: Re: [PVE-User] Ceph Cache Tiering > > On 10/10/2016 04:29 PM, Adam Thompson wrote: > > The default PVE setup puts an XFS filesystem onto each "full disk" > assigned to CEPH. CEPH does **not** write directly to raw devices, so > the choice of filesystem is largely irrelevant. > > Granted, ZFS is a "heavier" filesystem than XFS, but it's no better or > worse than running CEPH on XFS on Hardware RAID, which I've done > elsewhere. > > CEPH gives you the ability to not need software or hardware RAID. > > ZFS gives you the ability to not need hardware RAID. > > Layering them - assuming you have enough memory and CPU cycles - > can be very beneficial. > > Neither CEPH nor XFS does deduplication or compression, which ZFS > does. Depending on what kind of CPU you have, turning on compression > can dramatically *speed up* I/O. Depending on how much RAM you > have, turning on deduplication can dramatically decrease disk space > used. > > Although, TBH, at that point I'd just do what I have running in > production right now: a reasonably-powerful SPARC64 NFS fileserver, > and run QCOW2 files over NFS. Performs better than CEPH did on 1Gbps > infrastructure. > > -Adam > > Out of Curiosity, I suppose you're using the default 'NoCache' as the > cache mode of those QCOW2 images ? > > _______________________________________________ > pve-user mailing list > [email protected] > http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user _______________________________________________ pve-user mailing list [email protected] http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user
