running mksnap_ffs

[Willem Jan Withagen]

Kris Kennaway wrote:
......

>>> The file-system would come to a stop, processes stuck on bio, snap-shots
>>> not finishing etc.  This was caused by the system running out of usable
>>> buffers.  The change forces them to be flushed every so often.  This is
>>> independant of locking.  10 might be to aggresive.  Some scaling of
>>> nbuf would probably be better.
>> When I run mksnap_ffs it runs to the point where ANY access to the 
>> filesystem gives that process a lockup.
> 
> Yes, that is expected.  Actually it begins when something accesses the
> directory in which the snapshot is being made, since that causes the
> parent directory to be locked...then something tries to access the
> parent directory, which eventually cascades back to the root.
> 
>> Getting the file system back is only thru "hard reboot". Trying to do it 
>> the gentle way locks the whole system.
> 
> Or waiting until the snapshot operation finishes.  You (still) haven't
> determined that it's actually hanging as opposed to just waiting for
> the snapshot operation to finish.

True, and that is what I was refering to.

* I've let it run for 12 hours on 1,5T (that's why I asked for other
	experiences)
* I looked at diskstats with gstat:
	that turned out that everything was idle for > 5 minutes

Then I concluded that it was locked.

IF you can give me a fair estimate of time < 1 day I'll be willing to let it 
sit for so long. But I'm not going to wait forever. :)

--WjW