On 11/10/13 09:05, Adam Goryachev wrote:

On 11/10/13 17:52, Guillaume Betous wrote:

quoted

quoted

RAID6, preferrably with a spare.

I'm not comfortable with RAID 6 setup. What is the minimal number of
hard drives for having a RAID 6 + spare ?

Check wikipedia, but minimum of 4 drives for RAID6, consider 2 data
drives plus two redundant drives, allowing you to lose any two drives
(slightly better than RAID10 on 4 drives).

In direct answer, RAID6 + hot spare is a minimum of 5 drives.

That's just the /sensible/ answer.  The minimum is actually 4 drives -
one data, two redundant, and one spare (though obviously there are
better ways to use your drives).  And with mdadm, you can tell it that
three of these drives are missing.  While such things might seem a bit
silly, it is sometimes convenient to get your raid up and running with
the setup you want even if you haven't physically got the drives in
place yet - you can add them in later.