apparent filesystem-related hangs

[Eric Anderson]

On 04/21/07 21:51, Wes Morgan wrote:
> I have several filesystems built on top of a gconcat volume consisting of 
> 2 300gb and 1 500gb drive. The /usr partition constitutes the bulk of it. 
> The volume is sitting around 95% full, and twice I've had the system 
> become "hung" in what I believe are filesystem operations. It seems to 
> crop up when rtorrent tries to create files that would fill up the system, 
> but of course it doesn't actually reserve it until it is used. Any running 
> process remains responsive until it needs to access the disk.
> 
> The system was running a fairly recent 6.2-stable, March 29, but I've 
> since updated to the most recent -stable.
> 
> If anyone can give me some pointers as to how to tell exactly where these 
> processes are hanging, I can try to reproduce it... But it takes a while 
> to fsck the volume so I don't want to have to try too many things. If it's 
> not a known problem I can then submit a PR.


Output of a 'ps -auxl' would help a lot, since it will tell you what 
each process is doing.  Also, if it's really hung (does a 'df' or 
'mount' return?), then having DDB in your kernel config, and a valid 
dump device set up would allow you to get a dump (at the debugger 
prompt, do 'call doadump').  Once you have that, you can debug it much 
better while your system is back up doing other things.


I have a similar issue on one of my file servers, however I know it was 
caused by file system damage that fsck cannot fix.  My choice is to live 
with it, or dump/restore to a newly newfs'ed file system.  That's no 
fault of UFS of course (this was caused by disk issues).


Eric