[mythtv] Possible Future Option?

Bruce Markey mythtv-dev@snowman.net
Sat, 30 Nov 2002 00:45:38 -0800

Matt Zimmerman wrote:
> On Thu, Nov 28, 2002 at 11:49:02PM -0800, Jeremy Oddo wrote:
>> ...I was just thinking that it would be
>>cool to be able to define MULTIPLE paths (or an array of paths) and then
>>be able to select that "record to" path under the "settings" option...
> I understood fine, but I cannot think of a realistic situation where would
> be useful to me.  Why would you want to place different recordings under
> different paths?

Matt, first off, thank you for your efforts on this project.
I first installed from your Debian packages to check things
out before compiling from source. It was very reassuring to
have everything configured correctly for me and to see it
work on the first try.

There may never be a realistic situation where storing files
in different directories would be useful to you and I believe
that there are certainly bigger fish to fry. However, I too
thought this might be useful even before seeing Jeremy's post.

First, I'm using a machine with a 30GB disk. Root and swap
are at the beginning then a large partition where I put the
video files. I want more space so I'll probably get a 60-100
Gig disk. I may not be able to stripe the mismatched disks
together and may not want to even if I could. If I can only
write to one dir on the new disk I can't take advantage of
the free space on the current disk. Myth could choose to
start a new recording in the dir with the most free space
so the user doesn't need to worry about it.

Next, with multiple tuners, the performance might be better
if each file is streamed to one dedicated disk. The fastest
way to write a large continuos files is to position the
disk head and let it rip with the heads only making track
to track seeks at the end of each cylinder. Any RAID
scheme would cause more head movement for this specific
case even though RAID is much better in typical cases of
random reads and writes. Again, myth could choose the dir
with the most free space that is not already being used
for another recording.

I've been thinking about how to have tuners on separate
machines with each writing to its local disk. To do this
the 'recorded' table might need a column for the hostname
in order to locate the recordings. The path could also be
included in this table. Even if the path is not stored
in the database, the filename for a recording could be
searched for in each of the configured directories.

So, I second Jeremy's request but please don't put off
any of the great stuff being worked on now for this
little extra.

--  bjm