Big Linux software RAID using USB disks?

Solution 1:

While technically doable, I don't think its a very good idea - You will have difficulties tracking which disks are failing, the system will be cumbersome and prone to issues. 2.5" disks are not good value (per gig) compared with 3.5" disks. You will also likely have issues with stability of the RAID - both because of vibration and IO limits.

If I were tackling the problem I'd consider looking at a second hand NAS (with new drives), or Backblaze pods are not excessively priced and probably do what you want without a heavy premium.

IMPORTANT ADDENDUM

DO NOT USE RAID6 (or RAID5). These not scale well - the statistical chance of additional disks failing during a rebuild is surprisingly high with large disks (not to mention performance difficulties). Go for RAID10

Alternatively, I'd look for cheap computers with good 80+ PSU's, lots of hard drive bays and then use a distributed file system for redundancy and scaling - something like moosefs or gluster.