(How to) Replace a Hard Drive in a ZFS Pool

1st Official Post
    • New
    • Official Post

    Replacing a Hard Drive in a ZFS Pool


    Currently, the openmediavault-zfs plugin does not allow replacing a hard drive in a pool from the GUI. Therefore, the best way to do it is through the CLI.


    1. Quick Explanation of the Process


    There are several ways to replace a hard drive in a pool. Here, I'll explain one that works for virtually any situation. The steps are summarized as follows:

    • Identify the serial number of the drive you want to replace.
    • Shut down your server and physically replace the drive with another of the same size or larger.
    • Start the server, identify the newly inserted drive, and run the CLI command that will replace the hard drive in the pool. ZFS will handle the entire process.


    2. Real case: Replacing a Hard Drive in a Raidz1


    We started with a Raidz1 consisting of three 12TB hard drives. After some time, one of them displays errors. ZFS seems to fix it on its own, but I've been skeptical about that hard drive for a while, so I'm going to replace it with a new one. The current status of the pool is as follows:

    ZFS is already warning that something is wrong. The Toshiba hard drive is the drive to be replaced. In this case, it's easy to identify since the other two are Seagate, but in any case, the name of the hard drive in the pool already gives us the serial number: 90M0A01HFP8F, which we can use to physically identify it on the server.

    Without doing anything other than updating my backup beforehand, I shut down the server and physically replace my Toshiba hard drive with a new Seagate hard drive, in this case the same as the other two in the pool, although it wouldn't be necessary.

    The pool status after starting the server is as follows:

    The pool is degraded because a disk is missing, but it's still working. The disk I removed from the server is now identified in the pool as: 1055532610611156137

    To identify the newly inserted hard drive, I run ls -1 /dev/disk/by-id/ and the output is this:

    Code
    ls -1 /dev/disk/by-id/
ata-ST12000VN0008-2PH103_WR8008CY
ata-ST12000VN0008-2PH103_WR8008CY-part1
ata-ST12000VN0008-2PH103_WR8008CY-part9
ata-ST12000VN0008-2PH103_ZLW2KVBM
ata-ST12000VN0008-2YS101_WV7009YL
ata-ST12000VN0008-2YS101_WV7009YL-part1
ata-ST12000VN0008-2YS101_WV7009YL-part9
... (Here are the rest of the devices in the system that I have removed from the post)

    The new hard drive is clearly identifiable, it is the only Seagate in my system that does not have partitions. It's this one: ata-ST12000VN0008-2PH103_ZLW2KVBM whose serial number matches what was written on its label: ZLW2KVBM


    All that's left to do is run the command for ZFS to replace the missing disk, now identified as 1055532610611156137, with the new disk, which in my case will be /dev/disk/by-id/ata-ST12000VN0008-2PH103_ZLW2KVBM. Therefore, the command to run is:


    zpool replace -f DATA 1055532610611156137 /dev/disk/by-id/ata-ST12000VN0008-2PH103_ZLW2KVBM


    Where:

    zpool replace -f = Command that will cause ZFS to replace the hard drive

    DATA = Pool name (adjust it to your configuration)

    1055532610611156137 = Missing hard drive ID (adjust it to the output provided by zpool status)

    /dev/disk/by-id/ata-ST12000VN0008-2PH103_ZLW2KVBN = New hard drive ID.


    A short while after running this command, the pool status is as follows:

    ZFS is replacing the old Toshiba drive with the new Seagate drive and is automatically synchronizing the pool data to the new hard drive. The process will take a few hours to complete.


    The operation ultimately took about 12.30 hours, and the final result was this:


    Done. The hard drive has been replaced and the pool status is ONLINE, everything is in order. The entire process was executed without any problems with a single command.


    3. References


    Official open-zfs documentation -> https://openzfs.github.io/open…er/8/zpool-replace.8.html

    Guide to replacing a hard drive in a ZFS pool -> https://jordanelver.co.uk/blog…led-disk-in-a-zfs-mirror/

    Useful information -> RE: Help to understand proper ZFS disk replacement process

    omv-extras wiki -> The openmediavault-zfs wiki document is currently under development. When completed, it will likely describe this process among many others.

  • chente

    Approved the thread.

Participate now!

Don’t have an account yet? Register yourself now and be a part of our community!

Register Yourself Login