[TriLUG] stale NFS problem with RHEL 4.5 & NetApp Data ONTAP 7.0.6

[Jeremy Portzer]

This isn't directly addressing your issue, but if you do need to enable 
"noac" to turn off attribute caching, you could also enable "noatime" to 
stop the atime updating.  This could offset the performance cost of "noac".

Check to be sure your applications don't rely on atime for some reason 
though.

--Jeremy

Cristóbal Palmer wrote:
> Hi folks,
> 
> We've got a cluster of web servers, some of which seem to have an
> interesting problem:
> 
> [~]$ cd /path/to/docroot/of/vhost/html
> [html]$ ls -alh|grep for
> drwxrwxr-x  21 2197 20164 4.0K Sep 26 02:19 forum
> -rw-r--r--   1 2197 20164 3.8K May 14  2005 oeforums.gif
> -rw-r--r--   1 2197 20164 7.6K Jan 16  2005 oeforums.png
> drwxr-xr-x  18 2197 20164 4.0K Sep 26 02:14 oforums
> [html]$ ls -dalh forums
> drwxr-xr-x  18 2197 20164 4.0K Sep 26 02:14 forums
> [html]$ ls -alh forums
> total 287M
> drwxr-xr-x  18 2197 20164 4.0K Sep 26 02:14 .
> drwxrwxr-x  29 2197 20164 4.0K Sep 26 15:37 ..
> -rwxr-xr-x   1 2197 20164  29K Jan 15  2005 admin.php
> [about 20 more lines redacted]
> 
> So to parse the above for you:
> 
> I log into a web node and...
> (1) I cd to the docroot of one of our vhosts
> (2) I grep for anything in the docroot matching "for" and see several
> files and a directory called "forum" there. I do NOT see a directory
> called "forums" in this output. This is correct.
> (3) I explicitly ask to see the directory "forums" and I DO see
> something. This is NOT correct.
> (4) I explicitly ask to see "forums" and its contents and I DO see
> something. This is NOT correct.
> 
> The docroot is NFS (version 3) mounted. The NFS server is a NetApp. If
> I take a web node out of service, unmount and remount the
> filesystem... the problem goes away. An 'ls' will then correctly show
> no directory named "forums" in the docroot.
> 
> I'm told that changing our mount options could fix this. Proposals
> included setting "noac" or "actime=0" to either disable attribute
> caching completely or set attribute caches to have a validity of 0
> seconds, respectively. I'm worried that'll tank our performance. This
> little NetApp is already plenty busy.
> 
> Here are our current mount options for that filesystem:
> 
> rsize=8192,wsize=8192,intr,tcp
> 
> We have a ticket open with NetApp, but I'm hoping to get additional
> feedback from people who might be using CentOS or RHEL with a
> NetApp... people who might've run into this before and found an
> elegant workaround. :)
> 
> Cheers,