Re: btrfs-balance causes system-freeze on full disk

[Hugo Mills <hugo@carfax.org.uk>]

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On Tue, Oct 27, 2015 at 05:05:55PM +0100, Jakob Schürz wrote:
> Found a new habit...
> 
> I have a lot Snapshots on my drive. (Take every 10 Min a new one, every
> houry one, every day one, every system-update, every plugin after
> external HD...)
> 
> If there are to much snapshots (didn't find out the count how much
> exactly) balancing fails with a system-freeze.
> if i delete some of my snapshots, balancing is working...

   The whole machine comes to a halt, or just the balancing? If you
have lots of snapshots, balance can take *insane* amounts of time --
my big storage array, for example, takes about 60 seconds to balance a
data block group, and something like 4+ hours to balance some of the
metadata block groups. While it's "stuck" like that, it is actually
making progress, but it doesn't look like it.

   Hugo.

> Maybe this is a hint for bugfixing!!
> 
> Do you think?
> 
> greez
> 
> Jakob
> 
> Am 2015-10-21 um 22:51 schrieb Kyle Manna:
> > I had a number of similar btrfs balance crashes in the past few days,
> > but the disk wasn't full.  You should try tailing the system logs from
> > a remote machine when it happens. You'll likely see some bug info
> > before the system dies and becomes unusable.
> > 
> > The issue I encountered is described @
> > https://bugzilla.kernel.org/show_bug.cgi?id=105681
> > ᐧ
> > 
> > On Wed, Oct 21, 2015 at 12:38 PM, Jakob Schürz
> > <wertstoffe@nurfuerspam.de> wrote:
> >> Hi there!
> >>
> >> Is it possible, what i've recognized now. My system (debian) runs on
> >> btrfs, and i have a lot of snapshots on my hard-disk.
> >> Since some days my system freezes totally. I recognized, it always
> >> happens during btrfs-balance.
> >>
> >> So i deleted some of the old snapshots and tried another balance-run.
> >> Nothing happened... No system-freeze.
> >>
> >> System-freeze means: No Keyboard-action. The Mouse is frozen, the screen
> >> is frozen, no magic-sysreq, no ssh-login.
> >>
> >> Can btrfs cause such a freeze??
> >>
> >> greez
> >>
> >> jakob

-- 
Hugo Mills             | Darkling's First Law of Filesystems:
hugo@... carfax.org.uk | The user hates their data
http://carfax.org.uk/  |
PGP: E2AB1DE4          |

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