[mythtv-users] Storage Questions. LVM, RAID, NFS

[Douglas Wagner]

Having had this happen to me a while back I can tell you.

Without any special configuration MDADM is pretty silent.  Alot of
distributions have some nightly e-mails going to root that might include
mdadm information (typically a cat of /proc/mdstat), and I know there are
some 3rd party tools that will monitor MDSTAT for you, but by and large
you're pretty much on your own to my knowledge.

Replacing a disk is pretty easy.  Shutdown your system (unless you have
hotpluggable drives, in which case you can send me $3000 for the advice here
as I seem to need the money more than you do *GRIN*), and install a new disk
onto the raid controller.

When the system comes back up, MDADM should recognize the drive and add it
as "spare", using a command (don't know off the top of my head, do a man on
mdadm) you will add that drive  into your raid array and it will
automatically rebuild for you.  Not hard stuff.

--Douglas Wagner

p.s. I'm still a newbie to RAID6, given appropriate precautions though
(don't buy the drives all at the same time from the same source that are the
same model/run, etc.) it's unlikely that in 5+ disks you'll have two fail at
one time...RAID5 is still what most business runs I think (at least the one
I work for does).

On 5/1/06, Dean Wilson <dean.k.wilson at gmail.com> wrote:
>
> Thanks for your help!
>
> > RAID 4 is similar to 5 except that it uses a dedicated disk for the
> > parity information rather than striping it across all the other disks.
>
> Is this good/bad/indifferent for Myth?  Can I specify which disk gets
> the parity info?  (If so, since I'm likely to have to have a single
> PATA drive anyway (with the others being SATA), would it benefit me to
> specify this drive as the parity disk?
>
> > RAID 6 is basically RAID 5 but with two separate parity sets allowing
> > for failure of two drives (but with 2 drives worth of storage space
> > lost).
>
> Is this necessary?  As I understand it, as long as I don't have a huge
> array of disks, the likelyhood of more than two disks dying at the
> same time are low.  So as long as I replace the disk ASAP, I should be
> fine with only one parity disk, yes?
>
> Speaking of replacing disks, how difficult is it to replace a bad disk
> with mdadm?  (And how will I know if a disk has gone bad?  Will it
> limp along, or force me to replace it immediately?)
>
> Again, thanks for all your help!
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