I want to make a standard linux software Raid10 over 4 HDD. The server has 4HDDs, 2 pairs from different vendors in order to avoid batch problems.
I want to have the mirror over two different Vendors, and then the Stripe over the mirror pairs. I could do that by manually creating Raid1/0, but mdadm supports Raid level 10. I just cant figure out how the Raid10 is then handled and how the data is distributed.
mdadm --detail /dev/md10
/dev/md10:
Version : 1.2
Creation Time : Wed May 28 11:06:23 2014
Raid Level : raid10
Array Size : 1953260544 (1862.77 GiB 2000.14 GB)
Used Dev Size : 976630272 (931.39 GiB 1000.07 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Wed May 28 11:06:23 2014
State : clean, resyncing (PENDING)
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : near=2
Chunk Size : 512K
Name : phost:10 (local to host phost)
UUID : a3de0ad5:9e694ee1:addc6786:c4449e40
Events : 0
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 81 1 active sync /dev/sdf1
2 8 97 2 active sync /dev/sdg1
3 8 113 3 active sync /dev/sdh1
does not really give any information about that.
How it should be:
Raid 1 / Mirror over /dev/sda1 /dev/sdf1 and /dev/sdg1 /dev/sdh1
Raid 0 over the two Raid 1 pairs
Is it possible to do that with the built in "level=10", how can I see what pairs are mirrored?
Thanks a lot for you help
Best Answer
I can't find a anything that says if you create a RAID10 array of 4 devices then the mirrors will be (ab) (cd) or whatever. If you want to guarantee the placement then you can create a nested raid by first of all creating two mirrors then creating a stripe with them.
Create the mirrors
Then stripe them
So now /dev/md10 is a stripe of two mirrors and you know the location of each type of disk.