On Nov 30, 2016, at 3:40 AM, Kamil Jońca <kjo...@poczta.onet.pl> wrote:
> Rick Thomas <rbtho...@pobox.com> writes: > >> 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. > > I though about this, but I'm afraid about performance (calculating > control sums ). Needlessly? > KJ There’s a three-way tradeoff: usable space; performance; survivability. For my application (backups), performance is less important than space and survivability. The performance hit definitely exists, but I do not find it a problem. Of course, YMMV — “your milage may vary". Enjoy! Rick
