Several months ago I had an old 3TB hard drive (HDD) crashed on me. Luckily it was a hard drive that is primarily used for backup purposes, so the data lost can quickly be duplicated from source by performing another backup. Since it was not critical that I replace the damaged drive immediately, it was kind of left to fester until today.
Recently I acquired four additional WD Red 6TB HDD, and I wanted to install these new drives into my NAS chassis. Since I am opening the chassis, I will irradicate the damaged drive, and also take this opportunity to swap some old drives out of the ZFS pool that I created earlier and add these new drives into the pool.
I first use the following command to add two additional mirror vdev’s each composed of the two new WD Red drives.
sudo zpool add vault mirror {id_of_drive_1} {id_of_drive_2}The drive id’s is located in the following path: /dev/disk/by-id and is typically prefixed with ata or wwn.
This created two vdev’s into the pool, and I can remove an existing vdev. Doing so will automatically start redistributing the data on the removing vdev to the other vdev’s in the pool. All of this is performed while the pool is still online and running to service the NAS. To remove the old vdev, I execute the following command:
sudo zpool remove vault {vdev_name}In my case, the old vdev’s name is mirror-5.
Once the remove command is given, the copying of data from the old vdev to the other vdev’s begins. You can check the status with:
sudo zpool status -v vaultThe above will show the copying status and the approximate time it will take to complete the job.
Once the removal is completed, the old HDD of mirror-5 is still labeled for ZFS use. I had to use the labelclear command to clean the drive so that I could repurpose the drives for backup duty. Below is an example of the command.
sudo zpool labelclear sdb1The resulting pool now looks like this:
sudo zpool list -v vault
(Output truncated)
NAME SIZE ALLOC FREE
vault 52.7T 38.5T 14.3T
mirror-0 9.09T 9.00T 92.4G
ata-ST10000VN0008-2JJ101_ZHZ1KMA0-part1 - - -
ata-WDC_WD101EFAX-68LDBN0_VCG6VRWN-part1 - - -
mirror-1 7.27T 7.19T 73.7G
wwn-0x5000c500b41844d9-part1 - - -
ata-ST8000VN0022-2EL112_ZA1E8S0V-part1 - - -
mirror-2 9.09T 9.00T 93.1G
wwn-0x5000c500c3d33191-part1 - - -
ata-ST10000VN0004-1ZD101_ZA2964KD-part1 - - -
mirror-3 10.9T 10.8T 112G
wwn-0x5000c500dc587450-part1 - - -
wwn-0x5000c500dcc525ab-part1 - - -
mirror-4 5.45T 1.74T 3.72T
wwn-0x50014ee2b9f82b35-part1 - - -
wwn-0x50014ee2b96dac7c-part1 - - -
indirect-5 - - -
mirror-6 5.45T 372G 5.09T
wwn-0x50014ee265d315cd-part1 - - -
wwn-0x50014ee2bb37517e-part1 - - -
mirror-7 5.45T 373G 5.09T
wwn-0x50014ee265d315b1-part1 - - -
wwn-0x50014ee2bb2898c2-part1 - - -
cache - - -
nvme-Samsung_SSD_970_EVO_Plus_500GB_S4P2NF0M419555D 466G 462G 4.05GThe above indirect-5 can be safely ignored. It is just a reference to the old mirror-5.
This time we replaced the entire vdev, another technique is to replace the actual drives within the vdev. To do this, we will have to use the zpool replace command. We may also have to perform a zpool offline first before the replace command. This can be successively done on all the old drives in the mirror with newer drives with larger capacities to increase an existing vdev’s size.