When installing an mSATA SSD, I had the idea of reserving space for future use in case of eMMC failure, so partitioned it with sda1 sized to match mmcblk0p1 and sda2 taking up the rest of the device. I’ve had no problems either with the re-positioned 2.4GHz radio device or with setting up /srv to use sda2.
I’m now wondering whether it makes sense to add sda1 to the root file system as an additional BTRFS device and then balance/convert the pair of devices to a RAID1 mirrored pair. I’m supposing that mirroring the eMMC in advance like this would make things easier in case the eMMC fails at some stage in the future. Is this a crazy idea?