Re: [gentoo-user] experience thus far

[Marc Joliet]

Am Sat, 17 May 2014 08:08:17 +0800
schrieb William Kenworthy <billk@×××××××××.au>:

> On 17/05/14 04:15, Marc Joliet wrote:
> > So, a week has passed since my conversion to btrfs.
> >
> > So far there seem to have been no problems, my system has been running as if
> > nothing has changed :) . Which, as a friend pointed out, is how it should be.
> >
> > I don't think there is anything particularly interesting to mention in addition
> > to what I already wrote. I can just say that I think the effort was worth it.
> >
> > The one thing that I can tell from reading the past two weeks of the btrfs ML
> > is that the 3.15 Linux kernel series will contain lots of bug fixes (for
> > example in balancing, error handling, and send/receive), and that I will want
> > to use that sooner rather than later. Of course, the severity of the problems
> > varies, and a lot are triggered under odd, or at least uncommon, circumstances.
> > Still, its worth paying attention to.
> >
> > Also, a lot of problem reports I saw came from people using other volume
> > management below btrfs, interestingly enough.
> >
> > As for the future, I think I will wait a while, and get some experience with
> > btrfs first.  I suspect that by the time btrfs supports swap files, it will be
> > stable enough that I would consider converting my SSD to also use btrfs
> > anyway :) . Possibly before that, once I am fully convinced of btrfs'
> > stability, I will also convert my backup drive and switch to using snapshots
> > and send/receive to perform backups. Perhaps somebody will have written a
> > backup solution on top of snapshots by then.
> >
> > Have a nice weekend,
> >
>
> Don't forget to have a maintenance program - run a scrub regularly once
> a week or so - I have enough btrfs drives (22 qemu files, 4 WD Greens
> att) to see about one or two scrub fixable errors a week with no obvious
> cause, sometimes serious (in a critical file).  My experience is that if
> you ignore these errors they seem to increase over time resulting in a
> crash and burn.  Keep an eye on your logs as btrfs will list the errors
> there as well ("grep -i btrfs /var/log/messages").  For the ones scrub
> cant fix, delete the file and restore from backup.  Errors that require
> off-line fixing (btrfsck) are the ones where I have lost file systems -
> though I have not seen this in the last 6 months.

I did not forget about scrubbing, though so far I have run them manually (once
on Monday after a weekend away from the computer, and once tonight, both
without error). Nevertheless, thanks for the reminder and extra info :) .

BTW: I came across an interesting tool called dstat (indirectly while looking
for which package contained iostat, which was mentioned on the btrfs ML). With
"dstat -df", you can monitor the I/O of each individual drive. It's fun
watching them be used in parallel :) .

Anyway, with dstat I discovered that my drives have noticeably different
throughput. Of course, I might have deduced that earlier:

# btrfs scrub status -d /home 
scrub status for 472c9290-3ff2-4096-9c47-0612d3a52cef
scrub device /dev/sda (id 1) history
	scrub started at Sat May 17 00:23:33 2014 and finished after 2536 seconds
	total bytes scrubbed: 215.42GiB with 0 errors
scrub device /dev/sdb (id 2) history
	scrub started at Sat May 17 00:23:33 2014 and finished after 3519 seconds
	total bytes scrubbed: 216.32GiB with 0 errors
scrub device /dev/sdc (id 3) history
	scrub started at Sat May 17 00:23:33 2014 and finished after 2346 seconds
	total bytes scrubbed: 216.57GiB with 0 errors
scrub device /dev/sdd (id 4) history
	scrub started at Sat May 17 00:23:33 2014 and finished after 2346 seconds
	total bytes scrubbed: 215.68GiB with 0 errors

Boy, is sdb slow! I might replace it with sde, which is laying around as a
spare for now, and make sdb the spare instead.

> I am quite practised in restoring from backups because of btrfs :)

Haha :) .

-- 
Marc Joliet
--
"People who think they know everything really annoy those of us who know we
don't" - Bjarne Stroustrup