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

[Thomas M. Pluth]

I like this idea. I keep a certain amount of disk storage in my backend
(around 600GB), but I have space on my frontends, too.  Adding more space to
my backend isn't feasible, since I'm out of IDE and SATA connectors and PCI
slots, whereas I have free connectors and slots in the other machines.  I
don't like to leave more than my backend up and running when I'm away, or at
night, but those resources would be available when I'm home and watching TV.
Also, being able to add another mount point to use for videos or recording
is a great idea, since changing the size of an existing volume would mean
saving the data, reformatting, etc. (unless using XFS)

-----Original Message-----
From: mythtv-dev-bounces at mythtv.org [mailto:mythtv-dev-bounces at mythtv.org]
On Behalf Of Art Morales
Sent: Tuesday, September 07, 2004 7:52 PM
To: mythtv-dev at mythtv.org
Subject: [mythtv] Alternative to LVM/Raid for multiple disks?

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