[Ocfs2-users] ocfs2 hangs during webserver usage

[David Johle]

>I will try changing the logging to use separate files for a day or 
>so to at least see what effect it has with regards to this issue...stay tuned.


Okay, that was easy to test, and fail -- still plenty of lag 
situations.  As expected, the results agree with another test I did 
which was to shut down one of the two nodes to the point of 
unmounting the shared filesystem.

I believe the problem here is that actual chid processes of Apache 
locally sharing the logfile is just as bad as sharing across 
nodes.  Maybe perhaps that is the root cause of the problem, and the 
fact that additional nodes are affected is just consequential.

Michael Moody suggested not using prefork MPM, presumably for this 
reason.  I wonder, does the worker MPM "consolidate" all the writes 
from the threads within a worker into a single buffered write 
stream?  If so, I can see how having 32 threads per worker would not 
reduce the amount of writes to the logfile, but could reduce the 
amount of contending I/O requests by a factor of 32.  Is this the case?

Way back when we first transitioned to Apache 2.x we looked into 
using a better MPM, but had some necessary modules installed that 
were not thread-safe, and thus would only work with prefork.  I am 
pretty sure this is still a constraint for us at this point.