If you decide to stay away from ZFS, it still might be best, as I
understand it, to avoid RAID 5 specifically, unless your system
has a hedge against the "RAID 5 write hole". (Acknowledgment: not
an original opinion on my part; rather, advice which, over the
years, already gets posted to this list from time to time, IIRC).
I'm not claiming to be a RAID or RAIDframe expert, so I won't try
to explain the "write hole"; but suffice it to say that after
experiencing enough problems with RAID 5 (on less-than-rock-solid
hardware & in potentially flakey power-environments), my life was
improved by deciding to stop using it... This was on big "-ish"
disks at the time, though probably an order of magnitude smaller
than your current ones.
I believe RAID 1, RAID 10 & RAID 6 either don't suffer from
"write hole" issues or at least are less susceptible to them.
[I'd recommend confirming this via more reliable sources; not
stated here as fact]. So RAID 1 is what I now stick with on
RAIDframe generally, and I also use hardware RAID 10 & RAID 6 on
systems with applicable controllers.
Building on previous remarks that a 4-drive set-up isn't optimal
for RAID 5, it's worth adding that 4-drive set-ups *are* nicely
conducive to RAID 10 & RAID 6, and more feasible to align with
stripe & buffer size; though wouldn't include any hot-spares.
The "cons" of RAID 10 & RAID 6 (compared to RAID 5) are that they
- will only offer you ~14TB total storage (rather than your 4-
drive RAID 5's ~21TB)
- and AFAIK aren't directly supported by RAIDframe
- however, RAID 10 can be achieved by raidframe-on-raidframe,
at the slightly cumbersome cost of setting up & managing
three raidN devs (a RAID 1 of two RAID 0's -- or maybe a
RAID 0 of two RAID 1's, I forget which is RAID 10 & which is
RAID 01...)
The "pros" of RAID 10 are that it
- will still survive the loss of 1 drive, just like RAID 5; and
in uncommon cases, even that of 2 drives. I wouldn't bank on
the latter, however
- should be *really fast* for both reads & writes (comparatively
speaking)
The "pro" of RAID 6 is that it will survive loss of 2 drives,
provided you can get it working with RAIDframe... although I
believe it would be comparatively slow.
The above is all stated from perceptions & recollections, my
apologies if I have any errors in, e.g., objective facts. Again,
best to confirm anything critical your data might depend on from
more official sources.
Best, -D