On Tue, 30 Oct 2012, Tim Connors <[email protected]> wrote: > > if i had to guess, i'd say that there are probably some cases where LVM > > (with its nearly direct raw access to the underlying disks) would be > > faster than ZFS zvols but in most cases, ZFS' caching, compression, COW > > and so on would give the performance advantage to ZFS. > > Just make sure the sum of the zvols remains below 80% of the total disk > usage, I guess. ext4 + lvm can effectively use more than 99% of disk > space (I've done it for years), but the moment you try to do lots of > rewrites on a device on zfs, the lack of a free-space-cache that btrfs has > means that the highly fragmented nature of the remaining 20% of space > makes zfs completely unusable the first time you try it (multi-minute > pauses and 250kB/s write rates vs 100MB/s. I quickly bought new disks).
That's one of several bad reports I've read about ZFS performance on mostly full filesystems. But it shouldn't be a big deal. I've got some servers that are all less than 25% full which I plan to convert to ZFS, even with snapshots I doubt that they will go over 50%. For my home server I currently have 1TB of RAID-1 which is more than 90% full (really bad given all the different Ext4 filesystems some of which are 99% full). When I convert that to ZFS on 3TB disks it will be a lot easier and I won't have issues of filesystem A filling while filesystem B is empty. If I upgrade my home server from 3TB disks when they have 2.5TB of data instead of waiting until they have 3TB of data it won't be that much of a big deal. > I'm actually regretting my move to zfs because of it - I can hardly afford > to repeat the month it took to rsync the backuppc pool to zfs in the first > place. If ext4+md aint broke, don't fix it. Sure it sucked, but the > alternatives suck harder. Ext4+md is broken. Linux software RAID has no support for recovering from silent data corruption, not even on RAID-6. Such corruption is becoming more common as data volumes steadily increase. We need BTRFS/ZFS features for data integrity. We also need something better than Ext4 fsck times. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/ _______________________________________________ luv-main mailing list [email protected] http://lists.luv.asn.au/listinfo/luv-main
