Replacing a ZFS pool device with itself

I wanted to replace a disk in a ZFS pool (RAIDZ1) with itself. Or in other words, format the disk and have ZFS resilver it.

The general advice is to offline the device and replace it with itself:

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zpool offline POOL_NAME DEVICE_NAME
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fdisk /dev/disk/by-id/DISK_ID # write empty GPT partition table
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zpool replace POOL_NAME DEVICE_NAME /dev/disk/by-id/DISK_ID

This doesn’t work however. I got an error message that was something like:

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cannot replace <device> with <device>: <device> is busy

Solution

In order to make ZFS happy when replacing a device with itself, you need to run labelclear on it before erasing the ZFS metadata:

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zpool offline POOL_NAME DEVICE_NAME
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zpool labelclear -f DEVICE_NAME # need to -f because it's still part of an active pool
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fdisk /dev/disk/by-id/DISK_ID   # write empty GPT partition table
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zpool replace POOL_NAME DEVICE_NAME /dev/disk/by-id/DISK_ID