Re: mdadm - two questions

[Rick Thomas <rbthomas@pobox.com>]

Hi Kamil,

You’d get a bit more space by configuring your 4 drives as a RAID5 array (3TB usable for RAID5, vs 2TB usable for RAID10).  The downside of RAID5 is that the RAID10 (or the one LV with two RAID1 PVs — they amount to the same thing for this discussion) can survive loosing two drives at once — if they happen to be the right two drives: i.e. not both sides of a single mirrored pair — while RAID5 would not be able to survive any failure that involved two drives at once.  Either configuration would survive loosing any one single drive, of course.

If you want to be able to survive simultaneous loss of any two drives, you should look at RAID6, which would have the same usable capacity (2TB) as the RAID10.

Just my two cents…

Rick