BTRFS data integrity (CRC32c) and HDD data integrity (sector ECC)

I agree with vonbrand, btrfs is not yet to the maturity level of ext* or XFS or JFS to name a few. I would not use it on a laptop with precious data unless I have a reliable backup that can be done also on the go.

Btrfs can detect corruptions but it won't do anything more than reporting the detection unless you have an available uncorrupted copy of the same data, which means you either need RAID or duplication of data on the volume.

That said, I am considering using it (using RAID-1) for one machine, but I also do have Crashplan running on this machine!

For a long time, I have been using JFS on my laptop. One reason was the lower CPU usage compare to XFS or ext3 when doing file operations. I have never verified if it saved power consumption as well, but that was my assumption. I found JFS pretty stable and safe, never lost data while using it.

Assuming your SSD is faster for writes (and not just for reads), then there's an easy way to set this up with Linux's RAID subsystem. Say you're going to replicate /dev/sda1 (HDD) and /dev/sdb1 (SSD):

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 --write-mostly --write-behind=1024 /dev/sda1

--write-mostly means that the preceding device(s) will be preferred for reading, while the following devices will only be written to most of the time. --write-behind means that the write-mostly devices are allowed to lag behind; the parameter determines how large the write buffer is. You may want to tweak the write-behind parameter based on performance on your machine.

If you want to use your existing volume, you can convert it to RAID-1 with superblock format 1.0.

Drives already include their own integrity checks, so there's usually not much use for another one on top. The main problem with drive failure is data that becomes unreadable, not data that becomes corrupted. I don't know what the relative undetected error rate is for SSD and HDD, but I suspect that it's about the same (and thus not SSD vs HDD but between the particular devices), so there's no reason to assume that the data read back from HDD is more accurate. Btrfs and ZFS have optional filesystem-level integrity verification if you want that.