[mythtv-users] Shared filesystem that looks different to different machines

[John Finlay]

On 6/4/2014 4:21 PM, Raymond Wagner wrote:
> On 6/4/2014 1:40 PM, Joseph Fry wrote:
>>
>>             I don't believe that NFS would have any issue with nesting a
>>             mount inside another mount like this, after all the OS just
>>             treats it as another filesystem and every linux system I
>>             have ever seen does this (/dev, /proc, etc).
>>
>>
>>         NFS can have issues if you mount one NFS volume within another
>>         NFS volume.  If access to the lower volume is ever anything but
>>         100% stable, and the mount point for the upper volume is lost,
>>         bad things happen.  It's the same reason why you never use an
>>         NFS share for swap space.
>>
>>
>>     Mounting one NFS filesystem on another NFS filesystem has been
>>     commonly used from the beginning of NFS: diskless systems did this
>>     all the time.
>>
>>
>> I could see problems like Raymond describes if it were two different NFS
>> servers and you were nesting... but on the same server, I'd imagine that
>> if one went, the other would as well anyway.
>
> I've had issues even when using only one NFS server. The mountpoint 
> basically becomes a black hole. Any process that tries to touch that 
> branch of the filesystem is irrecoverably blocked (SIGKILL can't even 
> touch them), and the system can only be fixed by a reboot.

I've used NFS for 28 years and the only time I've experienced a hang on 
access is when the filesystem is hard mounted and the NFS server is 
down. Once the server comes up the filesystem is then accessible. 
Perhaps you were using a particularly buggy implementation of NFS.