Can I have two zpools using different ZFS version on one server?

I just upgraded from FreeNAS 0.7.2 to NAS4Free 9.1 and have an old ZFS pool imported. Freenas used ZFS v15 and Nas4free is using v28. I would like to wait a bit before upgrading, but have a new disc I would like to plug in before that.

I'm wondering if it's possible to have an old disk with zpool v15 and to configure a new disk to be zpool v28? As I understand upgrading takes place "by pool", so I believe this should be possible?

Sure you can. The version is a pool property:

# zpool get version ovs m1
NAME  PROPERTY  VALUE    SOURCE
m1    version   15       local
ovs   version   23       default

Note also that while upgrading a pool is generally a good advice, beware that after doing it you won't be able to import that pool on systems that do not support the new version.

Yes you can keep the old version.

However there are reasons to upgrade:

• the newer version has far more features
• you can still go back (as far as I see) to FreeNAS you just have to use newer version.
• to tell the truth v15 was a long time ago

But yeah you can keep the old version, no worries and no side effects to be expected.

EDIT Yes, but FreeNAS 8.3 supports v28.