RELENG_5, snapshots and disk lock time

Paul Mather paul at
Mon Mar 7 08:58:11 PST 2005

On Mon, 2005-03-07 at 15:21 +0300, Dmitry Morozovsky wrote:
> Dear colleagues,
> dumping the snapshot of 140G ufs2 fyle system under contemporary RELENG_5 I 
> found that during mksnap_ffs file system is unresponsible even for reading for 
> more than 3 minutes (it's on modern SATA disk with 50+ MBps linear transfer). 
> Is it normal?

Oddly enough, this happened to me last night on a RELENG_5 system.  In
my case, things were so bad that mksnap_ffs appeared to wedge
everything, meaning I'll have to make a trek in to where the machine is
located and press the ol' reset button to get things going again. :-(

The machine in question makes and mounts snapshots of all its
filesystems for backup each night via Tivoli TSM.  This has worked
flawlessly for many months.  Last night, I had many BitTorrent sessions
active on the filesystem that wedged.  I guess the activity broke the
snapshot mechanism. :-(  The odd thing is that it survived the night
before, when there were also BitTorrent sessions active.

I wonder how much activity mksnap_ffs can take?



PS: The problematic file system was not low on space, which could be an
issue for snapshot creation.
e-mail: paul at

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