[mythtvnz] File System for RAID-5

[Tim Gibson]

My 2 cent's...

Currently I have two 500G drives in RAID1 for family photo's, videos etc and
another two 1000G drives in a single 2000G LV for "backed up" movies, tv
shows etc.  Later I hope to get say 2 x 2000G drives or whatever is
equivalent when my LV is almost full (just under half full atm) and make
another RAID1 with a new LV on top, move data across then add my original
two 1000G drives as another RAID1 and extend the LV.  My machine has the
sata ports for this and I'm using an old ide drive for the OS, all I need to
do is back that up and almost perfect.

Does mean I could lose "backed up" movies etc but a slight trade off.
Everything is on a UPS so power goes out at least the machine will shutdown
without data corruption

Tim

2009/6/16 Steve Hodge <stevehodge at gmail.com>

> On Tue, Jun 16, 2009 at 11:54 AM, James Booth <james at booths.net.nz> wrote:
>
>>  I’m starting to lean towards RAID1 or RAID10. There is one thing that I
>> am not clear on with RAID1, maybe someone can help me here.
>>
>>
>>
>> I understand the RAID is created out of partitions, as opposed to physical
>> drives. Does this mean I can divide 3 x HDD’s into 6 equal partitions, and
>> then set up a RAID-1 solution that mirrors each partition on another
>> partition that resides on a separate physical drive? ie I don’t need an even
>> number of disks for a mirrored system? If so, how does adding in more disks
>> work?
>>
> You can build mdraid volumes out of partitions or whole drives. So yes, you
> can split each drive into two partitions and then setup 3 RAID1 volumes from
> pairs of partitions on different drives. When adding more disks you can
> degrade some of the arrays and use the resulting spare space to create a
> bigger array with the new drive. Eg, you'll start with the following (drives
> are 500GB, labeled A, B, C, partitions are 250GB):
> Array 1: A1 B2
> Array 2: B1 C2
> Array 3: C1 A2
>
> Say you get a new 500GB drive, 'D'. If you're willing to stick to 250GB
> arrays (rather than reconfiguring to 500GB arrays) you can add the new drive
> while ensuring that you always have two copies of everything. Partition the
> new drive into two 250GB partitions. Then add partition D2 to array 3 (so
> array 3 has 3 copies of the data). Once the array has sync'd you have:
> Array 3: C1 A2 D2
>
> Now remove partition A2 from array 3. Finally set up a new array using D1
> and A2. So you end up with:
> Array 1: A1 B2
> Array 2: B1 C2
> Array 3: C1 D2
> Array 4: D1 A2 (empty)
>
> If you're not worried about maintaining two copies of everything during the
> process you can do this: create a new array out of the new drive D. Set it
> up with a missing copy. Remove C from arrays 2 and 3. Set up another array
> with drive C and a missing copy. At this point you have:
> Array 1: A1 B2
> Array 2: B1 -
> Array 3: - A2
> Array 4: D - (500GB)
> Array 5: C - (500GB)
> Copy everything from arrays 1, 2, and 3 to arrays 4 and 5 however you like.
> Then delete arrays 1, 2, and 3 and add drives A and B to arrays 4 and 5.
> Once they sync you'll have:
> Array 4: D A
> Array 5: C B
>
> Expanding a (mdraid) RAID10 is not so easy but I recommend it if you're not
> likely to expand often as the performance can be much better. You can set it
> up so that a single filesystem is striped across the 3 or 4 drives without
> needing LVM on top.
>
> Cheers,
> Steve
>
>
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-- 
Regards
Tim, Donna and Erin Gibson
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