[mythtv-users] OT? Shuttle + ProRAID or Obsidian case for i3/i5 Myth BE ?

Raymond Wagner raymond at wagnerrp.com
Wed Sep 21 21:23:48 UTC 2011

On 9/21/2011 16:54, Travis Tabbal wrote:
> On Wed, Sep 21, 2011 at 2:09 PM, linux guy <linuxguy123 at gmail.com 
> <mailto:linuxguy123 at gmail.com>> wrote:
>     I'm not sure what to say.  I haven't had a HD fail in the last 10
>     years.  I'm not sure why I would need a RAID setup that would
>     tolerate multiple drive failures.

The issue with RAID5 is that you are putting everything into a single 
array.  If you have two drives fail, you lose everything, with no chance 
of recovery of any of it.  If you go with multiple RAID1 arrays, you are 
really not losing all that much storage, especially if you use the cost 
of the RAID card to instead buy more drives, and one array failure means 
you're only losing the contents of that one array.

> And you can get I/O bound very fast with recordings and playback in a 
> myth system using RAID, particularly a small RAID5 like you are 
> talking about. Performance of the array is about equal to a single 
> drive, add in all the seeks you need to keep up with and your 
> available I/O falls off fast. Using single drives in storage groups is 
> a better solution, IMO. If you really must archive the TV shows, I 
> would use 2+ drives for recordings in a Myth SG, then copy the 
> recordings off to a large, slower, array later.

That's what I end up doing.  Recordings go to a smattering of individual 
drives from 300GB to 2TB, while the commercial-clipped archive is on a 
5.25TB hardware RAID6 array.

Another interesting option would be using a ZFS volume, with multiple 
drives as independent non-redundant zvols, and then marking your 
recordings as needing two copies.  Files are not striped across multiple 
drives.  Read performance is exactly that of independent drives, and 
write performance is half that.  If you lose a single drive, ZFS makes a 
second copy of the lost files on one of the other drives.  If you two 
drives, you only lose those files that only existed on those two drives.
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