[mythtv-users] Recovering dead database + new RAID advice

[John Morris]

On Thu, 2012-06-28 at 17:59 -0500, digid myth wrote:
> I would not recommend putting the 2tb drives in a raid 5 for your
> media. There are multiple reasons for this. One the raid will take for
> ever to build in the first place. The chance of a drive going bad on a
> rebuild are very high with that large of a drive, especially once the
> drives start aging. From a power perspective you will have all the
> drives spun up at the same time. You still will not have any type of
> backup of you data if that is important to you. 

If you have things set to automatically run a resync weekly you raise
the odds of surviving a failed drive a lot.  If every block is being
verified to read every week you won't get bitrot so unless two drives
fall over dead in a week (power event) you are ok.  Of course it must
always be repeated that RAID is not a replacement for a backup strategy,
but for transient TV shows it would be pretty reliable.

But I hadn't though through the power implications.  Comes from dealing
with servers that run 24/7 anyway.  Interesting.  Rsync nightly to make
a backup copy would mean losing one day's recordings at most and cut the
power consumption almost in half vs a RAID1.  And being two separate
filesystems on two different drives you avoid the problem with raid of
filesystem corruption being fatal.  Only downside is the difference in
storage between RAID1 or a mirrored backup drive vs RAID5.  Ok, I'm
seeing where that would be a good thing, especially with the ginormous
size of modern drives.

The original questioner was only going to use three drives anyway so the
difference is small, making it even more compelling.  Yea, my
recommendation for him is put one drive in service as recordings, one
for videos, music, misc and use the third to back em both up with a plan
to put in #4 before #3 fills up from trying to backup twice its
capacity.  Unless power consumption and noise totally aren't an issue at
all, as in a backend in a closet, then I'd say saving up for drive #4
and starting out RAID5 is an option so long as the risks/rewards are
carefully considered.

And with that many drives, a hot swap enclosure is something to think
about.  They are designed to keep the drives safe and cool.  And they
make swapping drives so much simpler vs opening 'er up.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 198 bytes
Desc: This is a digitally signed message part
URL: <http://www.mythtv.org/pipermail/mythtv-users/attachments/20120629/c017ce7c/attachment.sig>