newfs locks entire machine for 20seconds

[Eric Anderson]

Dieter wrote:
>>> What *exactly* do you mean by
>>>
>>>> machine still locks up with no activity for anywhere from 20 to 30 seconds.
>>> Is there disk activity? (e.g. activity light(s) flashing if you have them)
>> Cant tell if there is disk activity its in a DC miles away ;)
>>
>>> Does top continue to update the screen during the 20-30 seconds?
>>>
>>> I'm thinking that newfs has queued up a bunch of disk i/o, and other
>>> disk i/o gets locked out, but activities that don't require any disk i/o
>>> (like top, once it is up and running) could continue.  Is that what is
>>> happening?
>> No all sessions totally freeze. I have top set to 1 second refreshes and
>> the clock literally stops and then 20-30 seconds later continues.
> 
> Wow!
> 
>> All sessions are via ssh not X if that's of interest.
>>
>> I could understand if IO to disk for other processes became slow but
>> everything including things like top just stop which is quite odd and
>> concerning.
> 
> Ok, new idea.  Your disk activity is via the network, and your sessions
> are via the network.  Could it be that something network related is saturated?


I saw this once before, a long time back, and every time I went through 
a debugging session, it came to some kind of lock on the sysctl tree 
with regards to the geom info (maybe the XML kind of tree dump or 
something).  I don't recall all the details, but it was something like 
that.

Eric