[mythtv-users] Software RAID

matthew.garman at gmail.com matthew.garman at gmail.com
Fri Mar 9 17:38:09 UTC 2007

On Fri, Mar 09, 2007 at 12:29:07PM -0500, MacNean Tyrrell wrote:
> I did mean to ask, do all my drives have to be the same size?  for
> Raid 5 (seems to be concensus best one for space saving with Raid
> that i can find on net).  Or if not do i need even numbers, ie
> 2x250gig, 2x300gig, etc. or can i have 1x320, 2x200, 1x250, etc?

For RAID 5, you *can* have drives of differing size, BUT, it won't
make optimal use of your space.  RAID 5 will essentially treat each
drive as though it were the size of your smallest drive.

For example, if you have 1x320 + 2x200 + 1x250, then your total
capacity would be: 
    - 4 total drives
    - minus one for parity
    - smallest drive is 200
    - total capacity: (4-1) * 200 = 600

Formula is (n-1)*c, where c=size of your smallest drive.

Of course, you can play games with partitioning and/or lvm to make
the most efficient use of your available storage.  But that kind of
defeats the whole purpose of RAID5.


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