[mythtv-users] Network storage fault tolerance (was Re: Myth autoexpiring brand new shows)

Michael T. Dean mtdean at thirdcontact.com
Wed Aug 27 00:41:42 UTC 2008


On 08/26/2008 06:40 PM, David Brodbeck wrote:
> Michael T. Dean wrote:
>   
>> Speaking of which, does anyone know of a way to make NFS tolerant of the 
>> NFS server's going down so that it will automatically unmount/remount 
>> the filesystems?
>>     
> Technically NFS is stateless -- if a server goes down, I/O requests on 
> that filesystem just hang until it comes back.

For me the hanging part works, but the "until it comes back," doesn't 
when there's a reboot of the server involved.  When the server comes 
back, it continues to hang.  I have to unmount (which gives errors 
because the server "isn't there"--even if it is).  Then, eventually, I 
just remount, and it works (though sometimes it seems to show multiple 
connections in the nfs *tab files).

>   No need to remount. 
> This usually isn't what people want, though, because it leads to lots of 
> applications sitting around in unkillable D states.

I'm mounting with:

rw,_netdev,rsize=8192,wsize=8192,hard,intr,actimeo=0

(from http://mythtv.org/docs/mythtv-HOWTO-23.html#ss23.10 , but with 
nfsvers=3 removed as it's not required on my systems).  But, after doing 
some more reading on nfs.sf.net, I switched it to use nfs4 (rather than 
3) because it's supposed to be more reboot tolerant.  Can't test while 
the backend is recording, but if it works, I'll try to remember to post 
the results.

Mike


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