What would be the best way to partition it?
Best ways questions are always hard since they depends on both opinions, and on the experience of the person setting it up. E.g. if you know ZFS inside out then ZFS is a very good choice rather than classic partitioning and filesystems. If you never used ZFS and you want to be able to access your data when something goes wrong then the ZFS learning curve is bad.
Having said that: I see these options:
- OS on SSD, both disks via mdadm (software RAID). Mirror the whole disk, then treat that as a regular drive and set up different partitions.
- OS on SSD, both disks via mdadm (software RAID). Use raid per volume. This way you can combine both mirrored volumes for data, and use other partitions in stripe (e.g. temp folders for a database. Or swap in either a stripe or two swap partitions, one on each disk). This is more flexible and more complex.
- Hardware RAID. This usually only works on whole disks.
- ZFS RAID, possible with the SSD as a cache device. Most complex solution. But if you know ZFS it can do wonders.
- Software RAID via LVM. Same as first two choices, but possibly compatible with a windows setup. Might be interesting in the case of dual boot and shared data.
I can configure the RAID 1 in the BIOS -
RAID 1 in the BIOS is often intel fake RAID. Basically software RAID tied to a specific generation of motherboards. Unless you have very good backups or a spare motherboard of the same generation I would not use this. (If you have several identical machines in an office and you can borrow one then go ahead. If it is your only PC is the same model, avoid)
but when I did so, I can't partition the second disk.
If by the second disk you mean the combined HDDs then something is wrong. Did you load the relevant drivers? (SSD as first disk, mirror as second disk).
If you meant that you do not see two separate HDDs anymore, then it is working as intended.