I'm experimenting a lot with mdadm lately and finding that regardless of how many drives I use, e.g. if I create a --level=10 with 6 or even 8 drives, it will only create 2 mirrored sets like it does with 4 drives where that's the only possible option. Example follows.
Command used:
Code:
mdadm --create /dev/md1 --level=10 --raid-devices=8 /dev/{sdc,sdd,sde,sdf,sdg,sdh,sdi,sdj}
Result:
Code:
Number Major Minor RaidDevice State
0 8 32 0 active sync set-A /dev/sdc
1 8 48 1 active sync set-B /dev/sdd
2 8 64 2 active sync set-A /dev/sde
3 8 80 3 active sync set-B /dev/sdf
4 8 96 4 active sync set-A /dev/sdg
5 8 112 5 active sync set-B /dev/sdh
6 8 128 6 active sync set-A /dev/sdi
7 8 144 7 active sync set-B /dev/sdj
Do I need to use nesting to achieve a stripe of 2x mirrors? Am I reading the result wrong - are they separate sets? (which would be very confusing and unclear). I'm trying to figure out if I'm missing a parameter or if this is expected behavior unless going nested.
Thanks.