[mythtv-users] Storage best practices in 2017

[Joseph Fry]

On Wed, Mar 22, 2017 at 3:06 PM Simon Hobson <linux at thehobsons.co.uk> wrote:

> Joseph Fry <joe at thefrys.com> wrote:
>
> > Personally, I wouldn't mess around with RAID, LVM, ZFS, etc.  Buy as
> much storage as you need for online use, and backup important data
> frequently to an offline drive that you store in a media safe (unless you
> can put a NAS at a friend/neighbors house and do offsite backups over the
> wire).
> >
> > I have used RAID in the past, and never had it save me once (have had
> good luck with drives)... while my backups have saved me many times when
> things were deleted or changed (something RAID wouldn't have helped with
> anyway).
>
> I would never consider building anything other than the most trivial and
> non-critical system without raid. If raid has never saved your bacom then
> you have been exceedingly lucky - it's saved me many times. Being able to
> restore from backups is one thing, but can't compete with a system that
> fails to die on disk failure, and can be recovered online (if you manage to
> swap drives without killing the system) just by partitioning a replacement
> drive and adding partitions into the array to be hot-rebuilt.
>

Perhaps I didn't fully qualify my response.  I wouldn't use RAID on my
mythtv server.  I have used raid extensively in my professional life.

RAID only really serves three purposes:
1. Performance:  Mythtv can use multiple recording drives and video storage
drives without issue... in most cases having several recording drives will
out perform a single raid array of an equal number of drives.

2. Uptime: Being able to hot swap a failed drive without taking down a
server is awesome.  But I don't treat my mythtv system as a critical
system.  My uptime is probably well over 99% without raid, and if I had to
take the system down for a couple of days to replace a drive, no big loss.

3. Space: RAID is great if you need to combine the volume of several
physical drives into one logical drive... but again, this is completely
unnecessary for Mythtv.

So, what do you gain by using RAID with mythtv?  Not much more than added
complexity and cost (for parity drives).  If you go with hardware RAID,
then you have other considerations, like what do you do if the controller
fails, not to mention even more cost.  Then you have to consider the
expense of spinning another drive just for parity.  And when you want to
add more storage, you can't just replace one drive with something larger
(well you can but you won't be able to increase the size of the array until
all of the drives are large enough to have the same size RAID partition)

I ran RAID (both hardware and software) for years when I first started with
Mythtv... was a great learning experience.  It was very reliable and I
believe I only had to resync the array a couple times due to drives acting
up (never a drive failure, just weirdness).  But since I decided to scrap
RAID 5 or 6 years ago I know that I will (likely) never go back.

If I have a drive failure tomorrow, I can almost guarantee that my mythtv
system will be 100% functional within minutes of my discovering the
issue... and any important data will be restored within a day.  And if I
chose to replace one (or more) of my 1TB drives with a 4TB drive the
process is about as simple as it gets.

Maybe I'm just getting old, but I much prefer only making things as complex
as is necessary to achieve my objective, and RAID is more complex than is
necessary.
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