I have 4 2.5" 7.2k drives lying about and I'd like to build some RAID arrays for a bit of VM storage on my KVM lab box.
There are 2x 320GB drives and 2x 500GB drives. I'm looking to create a RAID 10 array using 4x 320GB partitions. Then the remaining 180GB on the 500GB drives I'll build into a RAID 5 partition with another spare drive. I realise that performance will take a hit because there'll be contention on 2 of the drives in the RAID 10 array and using non-matched drives is also not-optimal but this is solely for a lab/test environment.
Initially I thought I would just create 4 matching partitions, create the RAID 10 array, LVM on top of that and done. But once I started looking into LVM on top of raid and 4k disks the subject of sector/block alignment came up and now I don't know where to start.
The 320GB drives report Sector size (logical/physical): 512 bytes / 512 bytes The 500GB drives report Sector size (logical/physical): 512 bytes / 4096 bytes
So from some reading there are the following variables that I need to take into account for this:
- Partition start/alignment
- RAID stripe size
- RAID superblock position (?)
- LVM PV --dataalignment
- then alignment of any file systems in the LVs
In some brief exchanges on IRC I have also received conflicing advice, that mdadm, the LVM tools and even fdisk are clever enough these days to take this into account and that I shouldn't worry. Is that the case?
Is anyone able to run through what I'd need to do in this specific case to get optimal alignment/sector/stripe size?
Please try and ignore the fact that the mixed drives mean the whole thing isn't optimal to start with, as I said, this is a test/lab environment.