This is mostly a note to myself.
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Edit: 2018.09.08 : If you see messages like this:
$ sudo gmirror insert swap /dev/da5p2 gmirror: Class not found $ gmirror list -a gmirror: Command 'list' not available.
You probably need to do this:
sudo kldload geom_mirror
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I had these drives:
=> 34 9767541101 diskid/DISK-653DK7WBFS9A GPT (4.5T)
34 6 - free - (3.0K)
40 1024 1 freebsd-boot (512K)
1064 984 - free - (492K)
2048 8388608 2 freebsd-swap (4.0G)
8390656 9758048256 3 freebsd-zfs (4.5T)
9766438912 1102223 - free - (538M)
=> 40 9767541088 diskid/DISK-4725K6DVF57D GPT (4.5T)
40 2008 - free - (1.0M)
2048 1024 1 freebsd-boot (512K)
3072 1024 - free - (512K)
4096 8388608 2 freebsd-swap (4.0G)
8392704 9758048256 3 freebsd-zfs (4.5T)
9766440960 1100168 - free - (537M)
=> 40 9767541088 diskid/DISK-4725K6ECF57D GPT (4.5T)
40 2008 - free - (1.0M)
2048 1024 1 freebsd-boot (512K)
3072 1024 - free - (512K)
4096 8388608 2 freebsd-swap (4.0G)
8392704 9758048256 3 freebsd-zfs (4.5T)
9766440960 1100168 - free - (537M)
=> 40 9767541088 diskid/DISK-652FK58FFS9A GPT (4.5T)
40 2008 - free - (1.0M)
2048 1024 1 freebsd-boot (512K)
3072 1024 - free - (512K)
4096 8388608 2 freebsd-swap (4.0G)
8392704 9758048256 3 freebsd-zfs (4.5T)
9766440960 1100168 - free - (537M)
=> 40 9767541088 diskid/DISK-653BK12IFS9A GPT (4.5T)
40 2008 - free - (1.0M)
2048 1024 1 freebsd-boot (512K)
3072 1024 - free - (512K)
4096 8388608 2 freebsd-swap (4.0G)
8392704 9758048256 3 freebsd-zfs (4.5T)
9766440960 1100168 - free - (537M)
=> 40 9767541088 diskid/DISK-653EK93XFS9A GPT (4.5T)
40 2008 - free - (1.0M)
2048 1024 1 freebsd-boot (512K)
3072 1024 - free - (512K)
4096 8388608 2 freebsd-swap (4.0G)
8392704 9758048256 3 freebsd-zfs (4.5T)
9766440960 1100168 - free - (537M)
They are involved in this zpool:
[dan@slocum:~] $ zpool status pool: system state: ONLINE scan: scrub repaired 0 in 15h30m with 0 errors on Thu Jul 27 18:34:28 2017 config: NAME STATE READ WRITE CKSUM system ONLINE 0 0 0 raidz2-0 ONLINE 0 0 0 diskid/DISK-653BK12IFS9Ap3 ONLINE 0 0 0 diskid/DISK-4725K6DVF57Dp3 ONLINE 0 0 0 diskid/DISK-652FK58FFS9Ap3 ONLINE 0 0 0 diskid/DISK-653EK93XFS9Ap3 ONLINE 0 0 0 diskid/DISK-4725K6ECF57Dp3 ONLINE 0 0 0 diskid/DISK-653DK7WBFS9Ap3 ONLINE 0 0 0 errors: No known data errors [dan@slocum:~] $
I decided to create a 6-way mirror for swap:
sudo gmirror label -v -b round-robin swap diskid/DISK-653DK7WBFS9Ap2
You will notice that the device named used corresponds to an item in the gpart show output but with p2 appended, as in partition 2. That is because partition 2 on each drive is my swap parition.
Then I added in each of the remaining drives, one at a time, but you can do them all on one line. For example:
sudo gmirror insert swap diskid/DISK-653BK12IFS9Ap2
At the end, I had this:
$ gmirror status
Name Status Components
mirror/swap DEGRADED diskid/DISK-653DK7WBFS9Ap2 (ACTIVE)
diskid/DISK-4725K6DVF57Dp2 (ACTIVE)
diskid/DISK-652FK58FFS9Ap2 (ACTIVE)
diskid/DISK-653EK93XFS9Ap2 (ACTIVE)
diskid/DISK-4725K6ECF57Dp2 (ACTIVE)
diskid/DISK-653BK12IFS9Ap2 (SYNCHRONIZING, 11%)
I added this to /etc/fstab:
/dev/mirror/swap none swap sw 0 0
The swap in /dev/mirror/swap corresponds to the name specified in the initial gmirror label above.
The last step is to activate that swap:
[dan@slocum:~] $ sudo swapon -a swapon: adding /dev/mirror/swap as swap device [dan@slocum:~] $ swapinfo Device 1K-blocks Used Avail Capacity /dev/mirror/swap 4194300 0 4194300 0%
That activation is done automatically at boot time, as specified by the entry I added to /etc/fstab.
