Question on gmirror and zfs fs behavior in unusual setup

[Octavian Hornoiu]

I currently have several storage servers. For historical reasons they have
6x 1TB Western Digital Black SATA drives in each server. Configuration is
as follows:

GPT disk config with boot sector
/dev/ada0p1 freebsd-boot 64k
/dev/ada0p2 freebsd-swap 1G
/dev/ada0p3 freebsd-ufs 30G
/dev/ada0p4 freebsd-zfs rest of drive

The drive names are ada0 through ada5.

The six drives all have the same partition scheme.
- They are all bootable
- Each swap has a label from swap0 through swap5 which all mount on boot
- The UFS partitions are all in mirror/rootfs mirrored using gmirror in a 6
way mirror (The goal of the boot and mirror redundancy is any drive can die
and I can still boot off any other drive like nothing happened. This
partition contains the entire OS.
- The zfs partitions are in RAIDZ-2 configuration and are redundant
automatically. They contain the network accessible storage data.

My dilemma is this. I am upgrading to 5 TB Western Digital Black drives. I
have replaced drive ada5 as a test. I used the -a 4k command while
partitioning to make sure sector alignment is correct. There are two major
changes:

- ada5p3 is now 100 G
- ada5p4 is now much larger due to the size of the drive

My understanding is that zfs will automatically change the total volume
size once all drives are upgraded to the new 5 TB drives. Please correct me
if I'm wrong! The resilver went without a hitch.

My concern is with gmirror. Will gmirror grow to fit the new 100 G size
automatically once the last drive is replaced? I got no errors using insert
with the 100 G partition into the mix with the other 5 30 G partitions. It
synchronized fine. The volume shows as complete and all providers are
healthy.

Anyone with knowledge of gmirror and zfs replication able to confirm that
they'll grow automatically once all 6 drives are replaced or do I have to
sync them at existing size and do some growfs trick later?

Thanks!