[mythtv-users] filesystem choice for an 8TB logical drive.

James Oltman cnlibmyth at gmail.com
Mon Oct 19 14:44:12 UTC 2009


On Mon, Oct 19, 2009 at 9:23 AM, David Knight <dlknight at sdf.lonestar.org>wrote:

> On Mon, October 19, 2009 1:34 am, Jean-Yves Avenard wrote:
> > 2009/10/19 Greg Grotsky <spikeygg at gmail.com>:
> >
> >>
> >> 1) plug in the new drive.
> >> 2) create a pv, vg, and lv on the new drive.
> >> 3) copy all the movies from the�jfs�drive to the new lv.
> >> 4) wipe the partition info and create and LVM partition on it.
> >> 5) extend the new lv onto the old disk.
> >> 6) extend the filesystem.
> >> (let me know if I'm missing anything here)
> >>
> >> Because of this I need to use a filesystem that can be resized.� I know
> >> that
> >> JFS can but I worry that it can not be shrunk (I'm not sure why).
> >
> > The more valid question may be, how likely are you going to want to
> > shrink a partition size?
> >
> > I run 5x 1.5TB in raid5 + LVM + JFS
> >
> > no trouble here
> >
> > one of my 1.5TB died after only 4 months, got it replaced under
> > warranty, glad I had RAID
> >
> >
>

I've had some issues with my RAID configuration in the past several months.
I was running 6 x 500GB drives in a RAID5 with JFS sitting on top.  It was
working fine until I had 2 drives detach from the array.  I was able to
rebuild the array and not lose much data thanks to JFS.  The fsck.jfs
replayed the journal log and saved most of my data.  This happened to me
several times and I lost my recordings directory along with some Documents.
I finally figured out this was all due to a couple bad drives that I got
replaced under warranty.  I was able to salvage most of my data after the
last (4th or 5th corrupted array) and saved it to a server at work.  I then
went about recreating my array as a RAID6 with 7 drives.  This whole setup
is running on an old Athlon 2800+ board.  The array creation was running at
around 12MB/s.  It was very slow.  But when the array rebuilt, I was able to
pull my data back, and it's been running well since.  That's been a couple
months.  However, because I have such a slow PCI bus, I'm having issues with
recordings and playing music through Myth.  Every once in a while, the
playback of a recording will hang.  After a couple of minutes, I get dumped
back to the recordings screen where I can start the recording over again.  I
can even FF to just before the point in the playback before the hang and it
plays just fine right through.  This also happens when I play back music.
The music will hang for a few minutes, then it continues.
The point I'm trying to make is, lots of drive space is GREAT, just make
sure that your mobo can handle the throughput.  I'm not really sure why
you'd want LVM to run on top of RAID.  That just sounds like extra
processing cycles.  You can expand RAID without much difficulty.  And
expanding the JFS partition is as simple as rebooting the box and your space
is available right away.  I'm pretty sure that my issues stem from the slow
mobo along with RAID6.  But I think it's worth having the extra protection.
Just food for thought.

Jim
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