System hanging during dump

Jeremy Chadwick koitsu at
Wed Oct 15 02:08:51 PDT 2008

On Wed, Oct 15, 2008 at 07:58:43PM +1100, Peter Jeremy wrote:
> On 2008-Oct-15 01:35:38 -0700, Jeremy Chadwick <koitsu at> wrote:
> >On Wed, Oct 15, 2008 at 07:24:28PM +1100, Peter Jeremy wrote:
> >> Last night, I attempted a full, compressed backup of my 181GB /home
> >> (on a PATA disk) to a remote system.  The backup started at 2159 and
> >> everything appeared normal until about 0040 when the system became
> >> non-responsive and this lasted until the dump completed at 1033.  This
> >> is the first full backup of /home I've made for several years (due to
> >> lack of space).
> ...
> >It's a known problem documented in my Wiki -- see "dump/restore".  Note
> >the part about UFS2 snapshot generation.  I'm almost certain this is
> >what you're describing.
> * UFS2 snapshot generation (mksnap_ffs, dump -L) takes too long; system is unusable during this time
>   In my case, snapshot creation took ~4 minutes.  The system was
>   running normally for 2.6 hours after snapshot creation completed
>   before it froze.

Did you read the References, including the one from myself?

Snapshot generation in some cases took only minutes, but *removal* of
the generated the snapshot took 1.5 hours or more, hanging the system
until the removal was complete.

| Jeremy Chadwick                                jdc at |
| Parodius Networking              |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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