Mixing unbalanced hardware in Software Raid

Hardware upgrades have left me with a bunch of 1TB drives. I was thinking about bonding groups of 3 together using old hardware and mixing the hardware raids into a larger software raid with some new 3TB drives....

I have most of the "junk" laying around and it would cost me approx $150US in misc hardware to put together 3 - 3TB raids (and as 2TB Drives become available maybe I'll move to 6TB Base units).
Then I then wanted to raid them together with some 3 TB drives in a larger software raid. Processor load in the box is not an issue. Up-time/Data safety is not a huge issue.
Don't get me wrong I want reasonable stability, but it is backups of backups aggregated in one place. That's one reason I want such large filesystems.

Any comments. Would the hardware raid and single drives be too unbalanced as to cause issues with a software raid? Would the same issue might arise using a group of say 3(7200 RPM Drives) with 2(5400 RPM Drives) of the same capacity in a RAID also?
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  1. Best answer
    I guess it depends what you mean by software raid issues.

    I would be amazed if any software raid implementation could be broken by performance differences of the raid components. What I'd expect to see is the performance being hindered by the slowest component in the array.

    You haven't gone into what raid types you'd use for all this. Given it's a backup of a backup is it so wrong to just JBOD all your disks together?

    Perhaps you'd JBOD the smaller drives to 3TB and then use two new 3TB drives to create a 3 x 3 Raid 5 array (6TB available). I'm not convinced such a system would be a good idea because at what point to you determine the JBOD array element is a bad idea? After it fails once? After it fails three times? Until you run out of smaller drives? What's the probability of any of the hardware raid controllers failing? What would you do if one of these did fail?

    You need to weigh up the cost in terms of configuration time and frame of mind with the cost of just buying new equipment.
  2. Best answer selected by pkn2.
  3. I broke down and bought a couple disks and tested it. Yes it is possible. Windows does not care about anything but balancing capacity across a raid. 2-3TB can be raided to 3-2TB you just end up with a few MB unusable on the larger hardware array.
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