[mythtv-users] Storage groups, NFS, and uniqueness

[Jim Stichnoth]

On Wed, Aug 19, 2009 at 5:41 PM, Michael T. Dean<mtdean at thirdcontact.com> wrote:
> On 08/19/2009 08:18 PM, Michael T. Dean wrote:
>>
>> On 08/19/2009 08:04 PM, Jim Stichnoth wrote:
>>>
>>> I have a master backend (mythmaster) with two drives, and the default
>>> storage group has two directories, one per drive.  I have a slave
>>> backend (mythfe3), which has a USB tuner and is diskless.  Its default
>>> storage group is set up to point over NFS to the master backend's two
>>> drives.
>>>
>>> Is there some way to let the system know that the storage groups on
>>> the master and slave backend are really the same, for the purpose of
>>> disk load balancing and free space calculation?  For example, the
>>> mythweb backend status page shows twice the amount of available space
>>> as there actually is:
>>
>> http://www.gossamer-threads.com/lists/mythtv/dev/392375#392375 and the
>> rest of the thread.  It's fixed in trunk, now.
>>
>> Unfortunately, the fix can't really be applied to -fixes (as it requires
>> modifying the protocol and a lot of new features).  In the meantime, you can
>> "unoptimize" your NFS (by setting the blocksize to 32kB).  If you do that,
>> make sure you remove that setting after upgrading to 0.22 (so you get better
>> performance).
>
> Actually, as this is likely to be an issue for a lot of users with current
> kernel configurations, Chris Pinkham has a different fix we can use for
> -fixes.
>
> Can you please post the output of:
>
> # On mythmaster:
> df -k /storage/recordings
> df -k /storage1/recordings
>
> # On mythfe3:
> df -k /net/mythmaster/storage/recordings
> df -k /net/mythmaster/storage1/recordings
>
> so we can decide on the specific value to use in our "engineering factor"?

Thanks.  I will try the "unoptimized" NFS.  Here is the df output, run
at the same time while no recordings were in progress:

[mythtv at mythmaster ~]$ df -k /storage/recordings/
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda4            949715108 703295484 198176832  79% /storage
[mythtv at mythmaster ~]$ df -k /storage1/recordings/
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sdb1            961432072 693664360 218929712  77% /storage1

[mythtv at mythfe3 ~]$ df -k /net/mythmaster/storage/recordings/
Filesystem           1K-blocks      Used Available Use% Mounted on
mythmaster:/storage/recordings
                     949715200 703295488 198177024  79%
/net/mythmaster/storage/recordings
[mythtv at mythfe3 ~]$ df -k /net/mythmaster/storage1/recordings/
Filesystem           1K-blocks      Used Available Use% Mounted on
mythmaster:/storage1/recordings
                     961432320 693664512 218929920  77%
/net/mythmaster/storage1/recordings

Another issue is that thanks to autofs, I often get reports like this:

Disk Usage:
...
    * MythTV Drive #3:
          o Directories: mythfe3:/net/mythmaster/storage/recordings,
mythfe3:/net/mythmaster/storage1/recordings
          o Total Space: -1 MB
          o Space Used: -1 MB
          o Space Free: 0 MB
...

It probably wouldn't hurt to probe the directory before doing the "df"
equivalent to be sure the directory is auto-mounted.

Jim