Partitioning 2 SSDs of different capacity for RAID 1

Question

I have two SSDs. One has 64G the other is 32G of size.

I'd like to create a RAID 1 configuration with Linux (it would be a software RAID), and I'm wondering if what I'm planning is possible or wise:

I think I'll cut the bigger drive into two 32G partitions, set up the RAID 1 to cover the 32G drive and the 32G partition, so whatever is going to be on this area will be mirrored on both SSDs.

What should I do with the leftover 32G partition?

Will it be still useful and visible?

Should I bother to create a Linux swap partition here?

Answer 1

That should all be fine. You can partition the extra space on the larger drive and use it for other things as you wish. I have a dev VM host here with two drives spilt into two, the first half as a RAID0 array (for speed rather than safety) for the running VMs and the other half as a RAID1 array containing the backups. Just be aware of the fact that activity on the other space will content for I/O bandwidth with activity on the RAID1 array (in the case fo my R0/R1 split the R1 array is only used when taking/restoring backups so there is little such contention in normal operation, though this will be less pronounced on SSDs than spinning disks as there are no head movements to worry about.

For swap space and RAID opinion can be divided. I keep mine on the RAID1/RAID10 array if present then if a drive dies your machine doesn't hang as soon as the kernel tries to access a swap area on that drive (instead of surviving gracefully as the other drive in the mirror handles the situation). This is slightly less efficient in normal operation though (which is what divides opinion) as any paging to/from disk activity has an extra layer of the kernel (the RAID management layer) to work through and writes need to go to both drives (though this is only an issue if your drives can potentially outpace the I/O bandwidth between CPU and your drive controller(s) it is somewhere where true hardware RAID wins - as far as the kernel is concerned it only writes once and the RAID controller handles the rest efficiently). A related note that doesn't affect your question: do not put swap partitions on RAID5/6 arrays as the write efficiency hit of such arrays will be significant if the machine needs to use swap heavily.