[baruch]

They get the same writes but not the same reads, so depending on the bug source it may not hit both at the same time. The read pattern itself may affect the way the writes are performed to the flash (delaying or speeding up writes pending for commit) that it may have a butterfly effect on the rest of the behavior and removing the disks from being in sync with regard to firmware bugs.

If you'd still follow up on your idea of using a read-only root like you did with CF cards and figured a safe place for the logs you could still use the SSDs in the same mode. Why not go that route?

[rsync]

Yes, depending on the bug source. But the bug source might be related to reads. Nobody knows. Splitting the risk across two different vendors / implementations seems to be good insurance.

[baruch]

I mostly handle server appliances and the read-only boot disk is bread-and-butter for anything I do. Bonus points for using initramfs and never hitting the boot disk after the initial boot is completed.

But if you stick to boot SSDs that are read and written to using different makes sounds like a good strategy.

[e12e]

It would of course be hard to avoid read-only flash no matter what you did - both bios and pxe rom from the ethernet card would presumably be read only flash today (that is writeable, but in practice only used for reading).