[mythtv-users] [mythtv] mike's description of how SG should be used

Michael T. Dean mtdean at thirdcontact.com
Wed Sep 15 08:36:57 UTC 2010

  On 09/15/2010 03:42 AM, Simon Kenyon wrote:
> i reading over the irc log from last night i came across the reference 
> by mike to 
> http://www.gossamer-threads.com/lists/mythtv/users/443158#443158
> i was not aware of this. i suspect that not many people are.
> having storage for recordings and videos on both my master backend and 
> a slave backend i had developed a strategy for working out where stuff 
> was:
> i have a master backend (called sanfrancisco) and a slave backend 
> (called newyork)
> on the MBE i have two mount points /myth and /myth2 and within them i 
> have
> /myth/sanfrancisco/recordings
> /myth/sanfrancisco/videos
> /myth2/sanfrancisco/videos
> on the SBE i have two mount points /myth and /myth2 and within them i 
> have
> /myth/newyork/recordings
> /myth/newyork/videos
> /myth2/newyork/videos
> i also have the two disks cross mounted on both the machines with NFS. 
> this was important in the days before SG
> i suppose my question is really; do the leaves of the tree, recordings 
> and videos in my case, have to be mount points for mike's strategy to 
> work? i realy hope not.

I'm not sure I understand the question you're asking, so I'll try to 
restate (more concisely) the point I was trying to make in that post 
regarding mount points:  when specifying directories for Storage Groups, 
never put a mount point directory name (the root of a mounted file 
system) in your SG directory list.

If you put a mount point directory name into an SG directory list, 
MythTV cannot tell when the file system is not mounted (the mount point 
and the mounted file system directory are identical), so it will gladly 
write to the parent file system (and possibly fill it up--which is 
/very/ bad if the parent file system is the system's root file system).  
Instead, always create one or more subdirectories within your file 
systems and put a subdirectory path into the SG directory list.  Then, 
when the file system isn't mounted, the directory doesn't exist, so 
MythTV will ignore it.

You've done that--since you're using subdirectories in your directory 
lists.  You're basically doing the approach described in the paragraph 

    If you prefer, you can do things slightly differently. Let's say you
    don't want to "re-use" directory names on your different backends
    because you may find it confusing to have 2 different file systems
    using the same directory path.

The only difference is that you have the host name within the mounted 
file system (but that's fine, too).

The rest of the post was just saying to only define your SG once on the 
master backend and don't override the directory list on the remote 
backends.  So, for you, create the Default Storage Group on the master 
backend with directories:


and Videos Storage Group with directories:


And you don't need the NFS mounts.  If you feel you must use them, just 
choose a Storage Group Disk Scheduler that takes into account local 
versus remote storage (i.e. Combination and maybe Balanced Disk 
http://www.gossamer-threads.com/lists/mythtv/users/424443#424443 .  
(That's the part I mentioned in the paragraph starting, "The only time 
this approach of never overriding Storage Group directory lists won't 
work..." (and ending with the discussion of the SG Disk Scheduler).

> is the above quoted post on the wiki? it certainly should be.

No.  Maybe I should put it there.  I have several other pages I keep 
saying I'll create on there, but haven't made time to do so.


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