[mythtv-users] network boot / boot speed (WAS: Re: diskless Mythtv USB)

[Tim Phipps]

On Tuesday 15 August 2006 22:43, gLaNDix (Jesse Kaufman) wrote:

> i'm definitely interested in this end of the setup of a diskless machine
> ... for those on the list that are doing diskless frontends this way,
> did you follow the instructions in the wiki?  what kind of boot speeds
> do you see?
My current setup is the opposite that you're planning but it might give you 
some ideas. I have one box next to the TV that acts as the MythTV back and 
front ends. It also acts as an NFS server for my desktop machine which is 
connected via wireless(11g). The desktop machine boots via PXE and shares the 
servers root disk (exported read-only). I've had to change a few files to be 
symlinks to a private directory for each machine so that each machine can 
have a different configuration. The server boots to runlevel 2, the client 
boots to runlevel 3 which also helps in running different things on each 
machine.
The client is a EPIA10000 running at 1GHz.  Bootup times seem slow but then 
they are when it boots off the local disk so the diskless thing doesn't add 
much delay. The average seek time for a 7200rpm disk is 8.3ms and ping times 
are about 2ms. Bandwidth is ~2MB/s which is much less than a local drive and 
is the main reason for the boot speed difference. If you can don't use a 
wireless link.

> i haven't sat down and timed mine from the hard drive, but 
> it's semi-decent i think ... running AMD Athlon64 3400+ with 512MB RAM
> ... same setup on the backend (which i would be booting the frontend
> from unless that's a terrible idea), except that the backend has 1GB of
> RAM ...
>

I've been experimenting on the diskless machine and I've managed to get a 
Debian Etch OS with a MythTV frontend down to ~250Mbytes. Since the diskless 
machine has 512MB RAM I've been able to tar up the OS image and after a bit 
of hacking on initramfs-tool scripts I've had it downloading the OS into a 
tmpfs RAM disk. The download and unpack takes about 40 seconds (much less if 
I had a cabled network) and after that booting is very fast since every file 
is already loaded in RAM. The system is very responsive since nothing ever 
gets paged out and it's silent (not even a case fan). Once the system is 
running there is about 150MBytes free RAM which is plenty for streaming video 
from the server.

I'd use it as the frontend by the TV but it's not up to being a backend as 
well so I'd have to put the backend in the garage and route a new aerial 
cable to that, then I'd need a new machine as the desktop machine for me to 
work on too.

Anyway, the point is with 512MB RAM you can get a frontend entirely in RAM, 
switch off the local disk and access your media over NFS. If you can 
underclock that processor you might be able to have a very quiet yet 
responsive frontend.

Cheers,
Tim.