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ZFS/Remove a vdev from a zpool.md

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+# Remove a vdev from a zpool
+
+https://www.truenas.com/community/threads/remove-a-vdev-from-a-zpool.35608/
+
+Funny how two minds can think alike, that is exactly what I did and I like to write it down for further generations to come (or myself if I do it again) ;)
+
+```
+# zpool status -v tank
+pool: tank
+state: ONLINE
+
+NAME STATE READ WRITE CKSUM
+tank ONLINE 0 0 0
+mirror-0 ONLINE 0 0 0
+gptid/e41b2476-22bd-11e2-ac2d-3cd92b06cdcb ONLINE 0 0 0
+gptid/e4c521be-22bd-11e2-ac2d-3cd92b06cdcb ONLINE 0 0 0
+mirror-1 ONLINE 0 0 0
+gptid/b4580a46-2fcd-11e5-af9d-3cd92b06cdcb ONLINE 0 0 0
+gptid/b51e45b8-2fcd-11e5-af9d-3cd92b06cdcb ONLINE 0 0 0
+```
+
+
+First you have to remove one of the new drives from the mirror.
+
+`zpool detach tank /dev/gptid/b51e45b8-2fcd-11e5-af9d-3cd92b06cdcb`
+
+Then, create a new pool on the just detached drive
+
+`zpool create sonne /dev/gptid/b51e45b8-2fcd-11e5-af9d-3cd92b06cdcb`
+
+Now replicate all your data from the old filesystem to the new. (snd/rcv can take a while)
+
+```
+zfs snapshot -r tank@nas_backup
+zfs send -Rv tank@nas_backup | zfs receive -Fv sonne
+```
+
+To make FreeNAS aware of your newly created filesystem
+
+`zfs export sonne`
+
+Then, while in the WebGUI, click "Storage -> Import Volume" to import it.
+Since I found no other way, I manually changed all path (user home dir, shares etc.) to their new values.
+Reboot.
+
+Then comes the scary part
+
+```
+zpool destroy tank
+zpool attach sonne gptid/b51e45b8-2fcd-11e5-af9d-3cd92b06cdcb gptid/b4580a46-2fcd-11e5-af9d-3cd92b06cdcb
+```
+
+Then the resilvering will set in. Done.
+
+**Reminder:** During the whole process, there is no redundancy. If any drive fails, your data is gone.
+
+*By the way, if anyone knows how to tell FreeNAS (or ZFS) to not use gptid in "zpool status", instead make it look like https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/zfs-zpool.html, please PM me.*
+