[mythtv-users] How to add more recording disk space: Christmas is coming !

Brad Templeton brad+myth at templetons.com
Sat Dec 18 19:51:18 UTC 2004

On Sat, Dec 18, 2004 at 10:30:30AM -0800, Bruce Markey wrote:
> Ah, that's the other side of the "/". As far as the server and
> interface is concerned, the filename are internal data and
> don't need to be human readable. Someone already wrote a script
> to create symlinks with readable names that point to the actual
> files.

Sounds useful, will check it out.  Since I often look at those files
it would be handy.  However, my perhaps incorrect impression was that
while the filenames were generated from values such as chanids, once
generated they were just long tokens and so they could be generated
with any other format, including showname-disambiguator etc.  The world
will live either way.
> I don't think there is any need to have separate physical spaces
> to have this kind of policy (in fact you'd be better off considering
> the total space). When cpinkham added auto expire, he deliberately

Generally you would.  The reason to consider separate physical space
is to deal with the concept of removable media, normally things like
USB disk drives, but quite possibly even a packet-level writable DVD
driver but that seems overkill.

For me, this is not a big feature, I am not one of those who loves
to archive, but there are folks like that who eventually will like
to see their system deal with removable pools of disk space.

Another type of "removable" space is an network mounted partition, in
that it may disappear at random.  People may find the desire to say,
"I would prefer this class of program go onto that network disk over

To get extreme, one could imagine that you mount your laptop on your
network.   You tell the system to record certain shows to the laptop
drive.   Then you take the laptop on the plane and watch them.

Hoewver, there are arguments that, other than the fact that it's
slow to do on demand when you are running to the airport, it may be
better to just transfer the shows to the laptop later.

This becomes a hoary problem that is easy to add too much complexity

> Let's say we use this disk by itself for a small news server with
> no binary groups and the average file size is 10k (which is
> probably high) and it writes randomly to the directories for
> newsgroups scattered across the disk (which doesn't account for
> the elevator algorithm). At 20ms avg seek, it can only move to
> 50 locations per second and at 10k per write that's only ~500kb
> per second.

Funny you mention news.  For reasons you cite, I first proposed a
format for USENET news servers that used continuous writing which
people picked up on and it has become a popular method!
> A better approach is the use a small disk for the system partitions
> (I use some old 4GB and 13GB disk for this on my system) and
> partition the big disk for video only with no other partitions, not
> even swap space.

More spindles are indeed good.  Of course, more ram can also solve
this problem as lots of buffering can avoid disk thrashing.

Today, I and others are trying to build leaner, low power, smaller, 
quieter, lower heat systems.   Unfortuantely that demands the opposite,
having fewer spindles.

Of course, one way to have extra "spindles" and still be quiet/low heat
is to use network filesystems for certain purposes.

Which doesn't invalidate what you're saying about the validity of having
a spindle just for video writing, it just moves it about.

However, as HDTV requires about 2 megabytes/second at most, you can
overcome a lot of thrashing if you just have lots of buffering.  And
memory is quieter that extra drives.

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