On Mon, Aug 08, 2016 at 02:05:47PM -0400, Robin Humble wrote: > I've 8G ram which should be heaps. limiting l2arc to 1G didn't help > either.
l2arc or arc? if l2arc, 1G isn't really worth bothering with and may even hurt performance. > actually, come to think of it, I could get logs out if ZFS locks up via > rsyslog to something lan/cloudy. I'll try that next time. yep, that or a serial console should do it. unless the kernel locks up completely before it can get out a log packet or output to tty :( > BTW does btrfs still have issues when the filesystem fills? does ZFS? In my experience, ZFS performance starts to suck when you get over 80% full. and really sucks when you get to 90+%. don't do that. that was on raidz (which inspired converting my backup pool from 4x1TB RAIDZ to to 4x4TB mirrored pairs). Haven't yet got to 80+% full with zfs mirrors, so don't know if that is as bad. > on my intel SSD, ZFS is noticably slower than ext4. part of it's > because of ZFS's poor integration with linux's virtual memory system > and both sets of caches clearly fighting each other, have you tried setting zfs_arc_min = zfs_arc_max? that should stop ARC from releasing memory for linux buffers to use. > but presumably it's slower 'cos it has more features (eg. checksum, > compression) too. compression usually speeds up disk access. The most likely cause is that ext4 has excellent SSD TRIM support but ZFS on linux doesn't. There's a patch that's (finally!) going to be merged "soon": https://github.com/zfsonlinux/zfs/pull/3656 there used to be another ZoL TRIM patch some time ago but it was scrapped to avoid duplication of effort with illumos/freebsd. interestingly, there's also a pull request for compressing arc and l2arc: https://github.com/zfsonlinux/zfs/pull/4768 depending on data compressibility, that should help a lot on low memory systems. craig -- craig sanders <[email protected]> _______________________________________________ luv-main mailing list [email protected] https://lists.luv.asn.au/cgi-bin/mailman/listinfo/luv-main
