[mythtv-users] Linux software raid question

[Yan-Fa Li]

On Thu, Jun 5, 2008 at 10:24 AM, David Brodbeck <gull at gull.us> wrote:
> Carl L. Gilbert wrote:
>> Getting it running is 1/2 the battle.  Having a recovery strategy is the
>> other 1/2.  Once you get that, then you should have confidence, not
>> before.  Not saying you don't have one.  But your text above is
>> highlighting only the setup part and not anything about recovery.
>
> With any RAID system your main recovery strategy should be a good
> backup.  RAID is mainly about protecting your uptime, not your data.  It
> will keep your system going if a drive dies, but if you get a corrupt
> filesystem or delete the wrong file the RAID array will faithfully
> duplicate the problem across all of the drives...

One possible path, which also helps with offline backups, is to make
use of LVMs snapshot feature.  Combining RAID5/6 with LVM and then
snapshotting the partition once a week for say 4 weeks and then
rotating those snapshots might give you a little bit more breathing
room for avoiding those "oh hell I deleted something I needed" moments
at the cost of using more disk space and some increased admin
complexity.

http://tldp.org/HOWTO/LVM-HOWTO/snapshotintro.html

It's not a substitute for full offline backups, but it's an
interesting compromise, but with disks past the TB size it's getting
hard to do backups on the cheap without a lot of extra work.

Yan