[mythtv-users] Is there a distributed filesystem available?

[Chris Henderson]

On 6/20/06, Debabrata Banerjee <davatar at comcast.net> wrote:
>
> The point would be to _not_ run RAID. I want to run a JBOD with a
> filesystem
> that doesn't go belly up with one bad disk, just loses the files that are
> on
> that disk. Mythtv recordings can just be re-recorded, the data isn't
> _that_
> important. However coming home to a completely broken MythTV blows.. Such
> things are possible, thought I don't know if possible right now in _linux_
>
>
Hi All,

Ummm RAID 5, is _exactly_ what you are looking for.
If RAID 5 is setup correctly you can lose one entire disk and the whole
system keeps RUNNING.

RAID 5 creates parity data that is stored in two different ways. the first
way is a little bit on each of the disks in the array. the second is to
create and online spare.
THe first way, if a disk in the array dies the other disks hold that parity
data for that disk. (dending on the raid card/config) The data for that
drive is still availale due to the parity data. UYes it is slower, as the
required data is then rebuilt on the fly and give out.

The second way, there is a spare disk sitting there and it is only used when
one dies. The first way is used more in SME (due to cost) and the Second way
is usd more in Large Enterprised. (cos they dont care about cost, to a
point)

THe problems with RAID 5 is that it can not be applied to the boot drive.
And it takes a minimum of three disk to create the array. But if you take
backups of mythconverg each day to the array then this is not a problem. You
can boot of a single drive and put the /Video, / , swap on the array if you
wanted to. Or there was a post not so long ago that delt with taking a
"Ghost" of the boot & / drive, so that when he was playing with myth, if he
broke it he would have a working copy to load, using a dvd. then just copy
over the DB backup to mythconverg and your away.

I setup this for a freind using 0.18.1 with the following arrangement.
p4 something or other
1gb ram
1 80GB HDD (boot, swap and root)
4 x 200GB HDD raid 5 for the /video partition. (if you foolow the "standard"
and place every thing under here)

So in then end when the computer boots it only will see two drives. the Boot
& / drive and the drive for the /video drive. the /Video drive will be close
to 800GB (you lose a bit for the parity data. upto one whole drive,
depending on the setup)

This was using a very good raid card that, acually was not that hard to
setup. I think he got it from work (large enterprise) so it must have been
supported under linux.

Anyway the other day (a month or so ago) i went over for a BBQ and the
myhtbox was in bits. I asked what was going on and he said that one of the
HDD died and he was replacing it. I watched him do it and all he did was go
into a BIOS type of thing for the raid card and told it to rebuild parity on
the new drive.
We came back about 4 hours later (and a lot of beers) and start watching dvd
on his system.

I think the best bit of this is that is OS independent. Other than the boot
drive everything is backed up by the RAID. This is how all the biggest most
high demand servers run.

Also the cost to do this is pritty cheap, and you dont need to mess with the


just my 2c worth.

CH
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