Yes, you can start a ZFS pool with a single drive in Proxmox and then add another drive later to set up a RAID 1 (mirror) configuration. This process is known as "disk expansion" or "pool expansion."
Here's an overview of the steps you would need to follow:
Create a ZFS pool with a single drive: You can create a ZFS pool
using a single drive in Proxmox by following the normal process for
creating a ZFS pool. The pool will start as a single-disk pool.
Add a second drive: Once the ZFS pool is created, you can add a
second drive to the pool. To do this, you would need to physically
add the second drive to the system and then use the zpool add
command to add the new disk to the pool.
Convert the pool to a mirror: After the second disk is added to the
pool, you can convert the pool to a mirror configuration using the
zpool attach command. This will cause ZFS to start mirroring data
across the two disks, providing redundancy and increased data
availability.
Keep in mind that adding a second drive to an existing ZFS pool is a disruptive process, as the data on the first drive will need to be copied to the second drive in order to set up the mirror. Additionally, you will need to have enough free space on the first drive to accommodate the data that will be mirrored.
It is also important to plan your disk configuration carefully before starting the pool expansion process, as you will not be able to add or remove disks from the pool once the mirror is in place.
