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 Yearling
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Jun
1
answered Does speed of ZFS snapshot rollback depend on number of files?
May
31
comment strange ZFS disk space usage report for a ZVOL
From everything I can see in this, it looks like a bug. The 'used' of a zvol with a volsize of 100G should not exceed much past 100G if there's no children or reservations or the like. Perhaps it was actually a 200+ GB volsize and you changed the volsize parameter? If not, FreeBSD-10.0 is not yet a production release; file a bug with them.
May
31
comment Tuning ZFS scrubbing, 141KB/s running for 15 days
More tuning may have helped, but not necessarily. It is important to note that a ZFS scrub rolls through the data structure, NOT sector by sector on the disks. Which is to say, depending on how the zfs data structure looks on your disks, a scrub operation may look incredibly random -- your disks may be capable of > 100 MB/s of sequential read, but completely random read will be another story entirely. Average block size would also matter here.
May
31
comment Does speed of ZFS snapshot rollback depend on number of files?
This question somewhat confuses me, as you sugest that you transferred a file using netcat @ 410 MB/s, then transferred zfs send/recv over netcat @ 70 MB/s. Then you also meniton ZFS rollback speed. Was the original transfer a zfs send/recv, or not? Where is ZFS rollback coming into play here?
May
29
comment ZFS performance: do I need to keep free space in a pool or a file system?
I grant you the reservation is no replacement for proper monitoring. I suppose it depends on the environment - one site was very worried because they'd previously had a user blow up a share massively over night due to a bug in some software they'd built, thus the reservation setting. Quotas would also theoretically stop that sort of thing, though, but they weren't interested in that. As for 85% and such; a lot of it is more about fragmentation.. if you can go 85% and back down without severe fragmentation in the process, yes, will be ok. :)
May
28
answered Nexenta - unknown trap type 8 in user mode
May
28
comment ZFS performance: do I need to keep free space in a pool or a file system?
Personally I use 70-75% maximum, not 85%. Edge cases can even degrade lower than that (I won't scare you with how much lower). You can in fact set a reservation to limit space.. this is common at some sites I know of. All you do is create a dataset, and set a reservation (or refreservation) on it that is equivalent to 25% of the total pool size, and poof, even if you use up every free block in your real datasets, you know the pool is still 25% free space, as you have a 25% reservation on there.
May
27
awarded  Editor
May
27
comment Tuning ZFS scrubbing, 141KB/s running for 15 days
Fair enough - added it all into the answer.
May
27
revised Tuning ZFS scrubbing, 141KB/s running for 15 days
per request, combining everything into answer
May
27
comment Tuning ZFS scrubbing, 141KB/s running for 15 days
This is pretty much completely false. CPU & RAM have effectively zero impact on scrub operations (assuming there's any free at all). Having lots of free RAM & CPU will not 'speed up' scrub operations. Scrub is limited by watching incoming I/O to the pool, not by checking for 'available system downtime', whatever that is.
May
10
answered ZFS iSCSI and free capacity in VMFS
May
9
comment Tuning ZFS scrubbing, 141KB/s running for 15 days
The %b and asvc_t reported imply some very, very random read workload going on (spinning disks should do better than that if it is truly sequential). First I'd turn on zfs_no_scrub_prefetch, to disable prefetch on scrub operations, just to see if that helped. If no joy, depending on the version of Nexenta you're on - you may be running 30/5, 5/1 or 10/5 (zfs_txg_timeout & (zfs_txg_synctime_ms*1000). Change zfs_txg_timeout to 10 and zfs_txg_synctime_ms to 5000, then try upping zfs_scan_min_time_ms to 3000 or 4000. This tells ZFS it can spend a lot longer on scrubs, may starve normal I/O!
May
9
comment Tuning ZFS scrubbing, 141KB/s running for 15 days
I should also read the entire question before responding - and stop browsing ServerFault while on conference calls. :)
May
9
comment Tuning ZFS scrubbing, 141KB/s running for 15 days
I suppose I should note that you modify these settings in bash using "echo <tunable>/W0t<number> | mdb -kw". And you view current values with "echo <tunable>/D | mdb -k". My notes say all of these can be changed in flight, none seem to require an /etc/system modification and reboot to take effect.
May
9
answered Tuning ZFS scrubbing, 141KB/s running for 15 days
Apr
15
awarded  Yearling
Apr
4
comment Are snapshots and clones filesystem-wide in ZFS-backed Lustre clusters
You've already answered your own question - no. I do have a question, though; what's your use-case, that you're after a distributed filesystem on Linux with CoW-like cloning and snapshots?
Mar
26
comment ZFS import pool ahcich0: timeout (NanoBSD 8.2 -> 9.1)
Does the pool still import fine on the old NanoBSD 8.2 USB stick? Because this just looks like a hardware error to me?
Mar
22
comment Accidently set chown “root” to all my server
I cannot vouch for this link, as I've never used it myself, but.. sysadminnotebook.blogspot.com/2012/06/…