Don't Understand ZFS Log Message

[n8n]

Hello,
This is probably a noob question. I went over to some zfs forums, but can't find info that I can understand about the message I get in the emailed system status report from N4F
ZFS pool status:
----------------
pool: vd00
state: ONLINE
status: The pool is formatted using a legacy on-disk format. The pool can
still be used, but some features are unavailable.
action: Upgrade the pool using 'zpool upgrade'. Once this is done, the
pool will no longer be accessible on software that does not support feature
flags.

Is this something that I can do, or is it within the programming of N4F?
Is this something that I should try to do?
Will doing the upgrade as recommended wipe the info on the pools - I should expect to reload the pools after the upgrade is done?
I'm about to create a second pool with 2 new drives - they've been formatted by N4F as zfs - I'm sure by checking the logs I'll know if I need to do the same task with those 2 new drives, but should I expect to?
Thanks in advance.

[crowi]

This was discussed already here:
viewtopic.php?f=66&t=5846

Did you recently upgrade to a newer version of N4F?
The 'new' 9.2.xxx has ZFS v5000, the older ones have ZFS v28
if you upgrade the ZFS you can't return to 9.1.xxx
So, the choice is yours.