[PVE-User] How to add mirror to existing zfs pool? What geometries are bootable?

[GM]

> - What is the correct procedure to add mirror to existing zpool so I have
> two mirrors striped layout?


Try 'zpool add -n pool mirror dev1 dev2' , that should reveal how the pool
would look like after adding those two devices. If satisfied with the
results, then execute same command without '-n' for the actual changes to
take effect.


> - Would pool with these two vdevs be bootable?


The pool itself would remain bootable given that the first pair of mirrors
still has the bootloader information on it. However you must ensure that
the new pair has the same bootloader information written on it as well, in
such way so that the system can boot from all 4 disks in the pool. How this
is done depends on how you currently boot the system (legacy, bios boot,
efi). I would personally clone the partition layout of the first pair of
disks onto the new pair by using sgdisk. Then add the disks to the pool as
shown above (by using the correct disk partition) and finally fix the
bootloader as per pve admin guide.