[mythtv-users] Adding extra recorder disk space for Christmas !

Brad Templeton brad+myth at templetons.com
Fri Dec 17 08:01:44 UTC 2004

On Fri, Dec 17, 2004 at 06:52:40AM +0000, Terry Barnaby wrote:
> I didn't think that the overlay file system was supported yet with the
> linux 2.6 kernels ?
> If it is where can I get it ?

I would be curious too, I thought those projects were mostly on hold.

In QNX, another unix-inspired OS with a microkernel architecture,
filesystems are inherently overlay, it's not a special filesystem.  In
unix/linux, when you mount a filesystem at /mnt, whatever files were
in /mnt at the time become invisible.   In QNX, they remain visible.

This seems to me the right behaviour, nothing special needed.  if you
wanted to mount on an empty directory you can do that.
> My first disk is 200G and the second disk is 200G. The first is full
> with recordings (although a lot will expire). I need to have 200+200G
> available for recordings, so I can't just mount the second disk over the
> first disks recordings directory.

If you had an overlay you possibly could, but anyway, with your 2 disks
equal you can just barely pull off the LVM switcheroo we described here.

However, the warning about xfs was an important one, you can't shrink it,
so you had better stick with ext2/ext3 for when you pull the disk.

You might, to be safe, want to have slightly less than 200gb on the
original disk when you do this, though in theory it could be full
and still do the giant move.   You have to move the files so you can
wipe it and convert it  -- or the video partition -- to lvm.

If your new disk were smaller than your old video, you could pull this
off if you had some other spare space you could grab temporily, perhaps
on a USB2 external disk -- those are getting really cheap now, I have
seen the cases for $30.   

Indeed, we might see people using USB2 disks for Myth routinely if
there were a way to allocate files to external disks down the road, as
the way to build the video library instead of burning DVDs.

You could for example, have a feature in myth to say you want to take
a recording offline.  It stays in the database, but the file is moved
to a removable medium (USB disk or DVD or CD-R).  You allow browse of
the archived materials, and when you pick one it says, "Go get
DVD #5" or "Get USB disk #2"

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