We have seen hanging clients on 7.3, not yet on RHEL3. The situation 
went worse when we switched to NFS over tcp. This could be explained by 
what Martin wrote about the kernel nfs layer loosing the packet. If the 
  tcp connection looses data midstream the mount is hung forever. We 
reverted to udp this afternoon and hope for better results.

Interestingly we went to nfs over tcp to work around the problem that 
Devin reports namely the slowdown and final lockup of the nfs servers in 
relation to local IO. Once we removed the backup client from the servers 
it was much better but it still happens once in a while.

Devin can you confirm that in the lockup all nfsd end up in D wait?

J

Devin Bougie wrote:
> Thanks Steve and Martin,
> 
> On Feb 10, 2005, at 3:41 AM, Bly, MJ (Martin) wrote:
> 
>> Having now read through the description of the problem (which wasn't
>> available to me when I created the problem description quoted below!), I
>> don't think it's the same problem as reported by Devin.
> 
> 
> Yes, I also agree these are separate issues.  The problem we're seeing 
> affects all nfs clients (Solaris, Tru64, linux, ...) accessing 
> nfs-exported filesystems hosted by a RH (RH9, RHEL3, FC3, ...) nfs 
> server.  We do also see this with or without LVM.
> 
> Devin
> 
>>
>> The problem we see is absolutely fatal and there is no way out -
>> processes do not complete and there is no I/O blocking as described...
>>
>> That said, I've seen LVM implicated in some NFS related fatal lockups of
>> a different variety.
>>
>> Martin.
>>