[mythtv-users] Reviving a myth system after hardware failure on /var

[Karl Newman]

On Thu, Nov 6, 2014 at 2:30 PM, UB40D <ub40dd at googlemail.com> wrote:

>
>
> On Wed, Nov 5, 2014 at 2:43 PM, Simon Hobson <linux at thehobsons.co.uk>
> wrote:
>>
>> But back to the OPs situation, it's a bit "post horse departed, closing
>> of stable door" suggestion - but RAIDing the OS directories would be a
>> great protection against this problem. On the first error, I think MD would
>> have thrown the faulty drive out of the array (for each partition/array
>> it's involved with as an error occurs in that partition) leaving the good
>> drive running.
>> Recovery from that is a matter of partitioning the new drive, and telling
>> MD to use it - then MD takes care of rebuilding the data onto it from the
>> good drive(s).
>>
>
> That's an interesting approach but I've never investigated software raid
> yet.
>
> If I do it over drives of different sizes, will I lose the extra space on
> the bigger drive?
> I have a bunch of drives in the machine and tend to upgrade them one by
> one, when they fill up or fail, with whatever the largest affordable drive
> is at the time of upgrade (nowadays 4 TB). So there will always be smaller
> and larger drives in there.
>
> Software RAID can work with partitions, but they need to be equally sized
(or, it will make the data on each device use the size of the smallest
device in the array). So you would "lose" the extra space in that it would
not be included in the array. You could partition and use that space
separately, though; it just wouldn't have the availability protection of
the RAID. It may make sense to leave the extra space "fallow" until you
have all the devices upgraded, then you could expand the partitions and
grow the array and filesystem to take advantage of the new space. But if
you really need the space, you could use the extra space on the larger
drive by itself, or you could create an additional RAID array (possibly
RAID 1 to mirror) as long as you had at least one other device the same
size or larger. Starts to get a little complicated then, especially when
you get rid of your smallest device and want to grow your main array. It's
not horrible, just a bit more complex and you have to keep track of what
you're doing and where your "active" data is.

Karl
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