[mythtv] Alternative to LVM/Raid for multiple disks?

Art Morales bioart at gmail.com
Tue Sep 7 22:51:42 EDT 2004


Hi All,

I just finished discussing this idea with a fellow Myther...  Right
now, there are two ways to add more disk space in multiple drives to a
mythbox: LVM and RAID.  I don't like the idea of LVM because the MBTF
is now decreased overall, and if I loose a drive, I loose the whole
volume.  Raid takes care of this, but now I'm either loosing ~30% of
the diskspace (Raid 5) or gain no redundancy (Raid 1 (or is it 0?)). 
Also, with Raid, I'm limited for the most part to equal size drives,
which is not what people have usually lying around, and makes adding
drives later kind of a pain.

Anyways, what if instead of having just one entry for video storage on
the backend, we allow multiple ones (/var/video1 /var/video2 etc.)? 
We could then add some very simple logic to the backend:  if less than
X gb on current disk, store on next disk, and so on.  I would assume
it would be a pretty simple addition to the code, but unfortunately, 
this programming is beyong me...  I don't foresee any significant
changes to the schema either...

The more I think about this idea, the more I like it because what if
instead of using local drives, we use network shares mounted on
diffent machines?  I have multiple desktops and servers in the house
and they all have extra diskspace.  If I shared this space and made it
available to the backend, I could suddenly have a 400gb store without
buying anything new... (basically acting as a distributed file
system).  On a simple gigabit network, there should be no issues with
bandwidth, even with HDTV content.

Once you have such a system in place, one could use cron jobs to move
certain files from one machine to the other and then transcode/process
them there on a faster CPU (since the backend is more likely to have a
slower CPU than the frontends).

Any takers?  I'm willing to help design the system a bit better if
needed, but my programming skills are not up to par (unless you are
talking Perl, then I can help :)

Art


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