[mythtv-users] Recording and Archive Storage Approaches

[Will Constable]

Regarding raid, I have just completed a setup like this.  I chose raid 3
because I'm using a somewhat antiquated PC without PCI-Express or Extended
and found a very sparse selection of raid cards that would work with PCI 32
bit.  I bought the PNY S-Cure Raid card and 5 300gb Seagate drives.
Performance wise, this works very well for recording and playing back

There is a catch-- possibly a problem with the pny card being extra
sensitive to power-- the first 48 hours of use I experienced several drives
falling out of array.  I proceeded to put the hard disks on a separate power
supply and tied the two power supplies' grounds together.  Since then I had
one incident where a drive fell out of array after I had been monkeying
around with the internals of the computer, so I'm hoping I loosened a cable
accidentally and that the setup will be reliable.  But either way- keep in
mind, you will probably need more power than you have unless this is a new
system.  My 400 watt PSU was not adequate for an athlon 2600+, gig ram, and
a total of 6 hard drives among other accessories.  

(BTW if anyone has suggestion about how to test/fix array reliability issues
like mine, please let me know)

Aside from that problem, having a 1.2 TB volume is quite nice, and
considering the prospect of burning 1200 Gigs to DVD isn't very pleasant,
the parity disk plus a good surge protector seems like an adequate level of
'backup' for my media files.  

I bet LVM would work but I don't know for sure... but if you buy a raid card
that is truly hardware raid, linux treats the array like an ide hard drive
and doesn't seem to be any the wiser that it's a raid system and not one big
drive.. so I would think that anything you could do with a typical drive you
could do with the raid array.

What file system do you plan to use?  I am curious-- using JFS myself, not
sure if there are better choices out there.

-will
 

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Chad
Sent: Monday, July 10, 2006 1:41 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] Recording and Archive Storage Approaches

On 7/7/06, Joel Turner <jturner421 at aol.com> wrote:
> I'm interested in upgrading my storage capacity on my Myth box.  After a
> month and a half , my hard drive is nearing capacity.  I currently have
> one PATA drive for OS and one 250GB SATA drive, XFS file system for
> recordings.  Tuners include one PVR-350, one Firewire, and HD over QAM.
> When I did my original install, I set up an LVM volume so adding drive
> capacity to the original volume should not be an issue.  After reading
> through the archives, it appears that there are many different thoughts
> on how to approach this. Relevant hardware is:
>
> Silverstone LC01
> AMD Athlon 3500
> Samsung 250GB
> EPoX EP-9NPA+Ultra
> Seasonic S12 430W
>
> The Silverstone has  6 3.5" bays, two of which are populated.  The EPoX
> will support 4 SATA drives without additional hardware.  I realize that
> this is only TV, but after going through two hard drive failures on a
> Tivo SA1, I am interested in being able to have some redundancy.  When
> you are three weeks behind on 24 and your hard drive crashes, spouses
> get very upset.  However I do not care if a show from Animal Planet or a
> sporting event is lost.
>
> So, I'm leaning towards doing the following.  I will add an additional
> 120GB drive that I have on hand to the 250Gb to add some more recording
> space. I'd like to establish a RAID 5 storage archive.  I plan to
> purchase 3 additional 250GB or 300GB drives.  The concept is that shows
> that I really care about can be flagged, transcoded and then moved to
> archive storage to be watched and deleted or retained. Other shows will
> remain on the recording drive and will auto-expire if necessary.  I do
> realize that RAID 5 is not a substitute for backup.  I will back up
> selective recordings to DVD.
>
> My questions are:
>
> 1) Has anyone else approached recording and storage in this manner?
> 2) Can I run multiple LVM volumes?  I'd like to run LVM over the RAID
> archive so it can be expanded.
> 3) Is it possible to move a show from the recording volume to the
> archive and still have it display in active recordings?
> 4) Will a RAID 5 array have enough speed to serve up HD content?
>
> Your comment and suggestions are greatly appreciated.
>
> --Joel
> _______________________________________________

I was holding off on answering this to see what other's had to say,
but here's my suggestion:

1.  I've thought about it, and almost implemented, but due to lack of
other interests, backgrounded this idea for the time being.

2.  Sure, you can have multiple LVMs, no different than having
multiple regular drives really.  RAID should be about the same, you
shouldn't have problems having multiple devices on your system, but
read on for more info.

3.  Sure, but from what I've read you'll have to do it outside of
myth.  You can manually move the files to your /mnt/raid directory (or
whatever you'll call it) and then symlink back to your recordings
directory (/mnt/store maybe?) like so:
mv /mnt/store/1021_200607101100000.mpg /mnt/raid &&
ln -s /mnt/raid/1021_200607101100000.mpg /mnt/store/

But you could make it easier by creating a small simple script that is
executed nightly and checks for all new recordings, moves them, and
then does the symlink for you.  I'm not going to build one because I'm
far from a decent shell scripter, but if no one else helps with that,
you can check the Bash HOW-TO for more info on shell scripting.

4.  Sure.  I've read (but never implemented) about something like a
5+1 RAID which implements both worlds, you may consider that route as
well.

Good Luck!

-Chad
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