[mythtv-users] thoughts on a combined backend/NAS box?

[Joseph Fry]

> > >
> > > I'll just put out there that no one in their right mind should ever use
> > > RAID5.  It's just not safe.  I'd recommend at least RAID6 or possibly
> > > RAID10 if you're paranoid.  Remember, if a disk fails in RAID5, you
> need to
> > > resilver the array.  That can take time.  What if another disk were to
> die
> > > during the resilver?  You'd be screwed.  And don't think it won't
> happen to
> > > you.  It happened to me.  It was awful.  Luckily, I managed to grab
> most of
> > > my data.
> > >
> >
> > There is nothing wrong with RAID 5... but you have to be aware that it
> > cannot be used in place of a backup, just like any RAID solution.  The
> odds
> > of a two disk failure are far lower than a single disk... so while the
> > potential is there, odds are it won't happen and in the meantime your
> > system will keep chugging along while the array rebuilds.
>
>     A single RAID 10 array still lacks sufficient redundancy and isn't
> really
> any better than a RAID5 array.


RAID 10 is somewhat better than RAID 5 as far as redundancy because it can
handle 1/2 the array failing (as long as it's the right 1/2)... but
"sufficient redundancy" is entirely dependent upon the use case.  I argue
that for a typical mythtv system with a good backup of critical data, any
level of raid (less raid 0) is overkill.  That's why I only raid my OS and
database, and I mirror it over 3 drives.


> You really need at least 2 copies of your data
> if you really care about it. Nothing short of this is going to be really
> any
> improvement. It will just be more expensive.
>

If your running a critical system in a high availability environment...
sure 2 copies is good.  I could argue that you really only need one copy...
a tested offline backup.


>
>     Ragging on one variety of RAID versus another is really just polishing
> the brass on the Titanic.


Agreed.  Every RAID variety has strengths and weaknesses... and it's more
important to focus on identifying and meeting an objective rather than
harping on about the various levels.  If you want the ultimate redundancy,
you don't use RAID at all... use some sort of redundant file system
spreading the storage across multiple systems at multiple sites
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