On 06/02/16 14:58, John Rumm wrote:
I seem to be sinking under a pile of spare hard drives at the moment -
typically 2.5" 500GB ones. It would be nice to find a way of making use
of them *cheaply*. It would be nice to build a NAS platform for use as a
backup repository, and for perhaps archiving stuff like films.

Performance is not that critical, but I would like fault tolerance. Not
too fussed about uptime. So it needs to be a RAID setup of some sort
that can survive any individual drive failure (e.g. RAID 5 or 6), but it
can be shutdown for maintenance etc without any worries - so I don't
need to worry about hot swap or redundant components.

A small low power mobo in an old PC case could be a starting point, or
for that matter, even as RaspPi 2 B or similar level single board
computer, but that will soon run out of sata ports (or not have any to
start with). One option that springs to mind would be a powered USB hub,
and a bunch of drive caddies which would be a cheap way of adding lots
of drives if required.

That then raises the question of software to drive it... How workable
would the various MD style RAID admin tools and file systems be at
coping with drives mounted on mixed hardware interfaces - say a mix of
SATA and USB? Has anyone tried multiple budget SATA cards on stock PC
hardware?


Linux MD (RAID) does not care what the interfaces are - it works at the
block device level, so as long as your devices appear, it will work find.

But of course you are going to have to balance the sizes for RAID1,5,6
which might not be totally convenient. MD RAIN can work with partitions
(it's just another block device) so that is one get out.

However, ZFS might be a more interesting choice.

For something like this, I would (and do) use Debian. ZFS is pretty
solid on Debian (but is not "native: you need to include an extra
repository http://zfsonlinux.org/debian.html ) and MD + LVM is
absolutely rock solid.