[mythtv-users] Install Mythbuntu with RAID 1 (Software)

[Robin Hill]

On Thu Dec 15, 2011 at 09:00:43AM +0000, Richard Morton wrote:

> >
> >
> > Well, the setup i have are 2 x  1 TB Hdd.
> > And i wanted to mirror 1 to the other.
> > So i would end up having the OS and the recordings on the same hdds.
> > I would use different partitions if that does work with RAID.
> >
> > After all if i get a third hdd for the os i might end up with an
> > unfunctional system if the OS HDD  crashes.
> >
> 
> 
> If that is what you are desiring then go buy a small SSD card for the OS
> (or two - or two old small 40GB drives).
> 
> RAID1 requires both drives to write the same information to both discs,
> which means you get zero performance benefit on write compared to a single
> drive and Myth requires write performance.
> 
> When reading RAID 1 also needs to read from both drives and compare the two
> sets of data to ensure that they are the same and not corrupted... again
> little or no performance gain.
> 
Err, no. There's no checking done in Linux software RAID (and I've not
seen it in any hardware RAID I've used). Reads are done from whichever
mirror is closest to the required position, and concurrent reads will go
to separate mirrors. If you want to verify the data, you need to run a
separate check process on the array.

> In effect you have a redundant system with the performance of 1 drive being
> used for OS and recordings and the collective experience and advice of
> almost everyone on this list is - don't share the same drives for OS and
> recordings...
>
That's definitely good advice though. In the parent's case, I'd
recommend getting a separate small drive for the OS & database, then
doing a regular rsync to a partition on one of the larger drives. That
way you have a fallback position if the smaller drive fails, giving the
redundancy wanted. I'm doing this myself, using an SSD for the OS &
database, but regularly synced to a standard HDD for if the SSD fails
(as it has twice now).

Cheers,
    Robin
-- 
     ___        
    ( ' }     |       Robin Hill        <myth at robinhill.me.uk>  |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |
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