Re-create special vdev mirror

kuruption · Aug 15, 2023

I had two SSDs setup as mirrored metadata vdev on a pool, and one disappeared.... looked "disconnected" in the webui, and I offlined it. Oopsie, now I'm down to a single drive in my special vdev, and I want to fix that.

Two options --

1) Can I add the second drive as a mirror to the existing special vdev? If so, how would I go about this (assuming CLI)?

2) Would it be safer/better to offline/disconnect the current, single disk in the special vdev, and then re-attach as a mirror? Some google said this could cause issues on the pool, but want to make sure.

Any other option here? I've tried adding two new drives in a mirror into the special vdev, but this resulted in an error (i.e., couldn't have a stripe and mirror vdev in special)

Running TrueNAS Scale 22.12.3.3

Pool info:

Code:

pool: vader
 state: ONLINE
  scan: resilvered 1.13M in 00:00:01 with 0 errors on Tue Aug 15 20:39:11 2023
config:


        NAME                                      STATE     READ WRITE CKSUM
        vader                                     ONLINE       0     0     0
          raidz2-0                                ONLINE       0     0     0
            78aefec9-a81b-11ea-82bb-0026b942e0cc  ONLINE       0     0     0
            79659516-a81b-11ea-82bb-0026b942e0cc  ONLINE       0     0     0
            797c9eda-a81b-11ea-82bb-0026b942e0cc  ONLINE       0     0     0
            7993ff4a-a81b-11ea-82bb-0026b942e0cc  ONLINE       0     0     0
            799d506a-a81b-11ea-82bb-0026b942e0cc  ONLINE       0     0     0
            79a1ba46-a81b-11ea-82bb-0026b942e0cc  ONLINE       0     0     0
          raidz2-2                                ONLINE       0     0     0
            c5e2f423-3f25-4c96-9b52-58b15a19fb19  ONLINE       0     0     0
            e0f272df-3ea9-4d17-935c-1ca87e66e5f6  ONLINE       0     0     0
            3d36552f-a468-429b-860d-17911500f799  ONLINE       0     0     0
            0d0d5fa5-047a-4fb3-8be3-f8fc8764cd83  ONLINE       0     0     0
            e6d6e5ca-ec70-47cd-b582-71f9804b1a8a  ONLINE       0     0     0
            2a93a080-140e-4817-830c-f290d1ecc932  ONLINE       0     0     0
        special
          f2a9eeab-3581-489c-8094-d038114901ab    ONLINE       0     0     0


errors: No known data errors

sretalla · Aug 16, 2023

kuruption said:
1) Can I add the second drive as a mirror to the existing special vdev? If so, how would I go about this (assuming CLI)?

Maybe even in the GUI, from the Storage screen, Manage Devices, click that device and use Extend (if that's available).

Otherwise, use zpool attach poolname existingDevice newDevice (where you replace those last bits with the gptid of the partitions you want to use as the source and new mirror)

sretalla · Aug 16, 2023

kuruption said:
2) Would it be safer/better to offline/disconnect the current, single disk in the special vdev, and then re-attach as a mirror?

I don't think you can do that.

kuruption · Aug 16, 2023

sretalla said:
Maybe even in the GUI, from the Storage screen, Manage Devices, click that device and use Extend (if that's available).

Otherwise, use zpool attach poolname existingDevice newDevice (where you replace those last bits with the gptid of the partitions you want to use as the source and new mirror)

Thanks, the attach command worked... I didn't like the "extend" button because it infers... a stripe or jbod kind of addition, but after checking the man page, the attach would create a mirror.

Patrick M. Hausen · Aug 16, 2023

You did create a partition table and use the gptid to refer to the device when attaching, right?

sretalla · Aug 16, 2023

kuruption said:
I didn't like the "extend" button because it infers... a stripe or jbod kind of addition

Well, as I said, that's the button that gets you the wanted result.

I have a bunch of older threads where I mention that Extend should not be the wording used for that button, it should say Attach.

I never got around to raising a request to have it changed.

vader · Jan 23, 2024

kuruption said:
I had two SSDs setup as mirrored metadata vdev on a pool, and one disappeared.... looked "disconnected" in the webui, and I offlined it. Oopsie, now I'm down to a single drive in my special vdev, and I want to fix that.

Two options --

1) Can I add the second drive as a mirror to the existing special vdev? If so, how would I go about this (assuming CLI)?

2) Would it be safer/better to offline/disconnect the current, single disk in the special vdev, and then re-attach as a mirror? Some google said this could cause issues on the pool, but want to make sure.

Any other option here? I've tried adding two new drives in a mirror into the special vdev, but this resulted in an error (i.e., couldn't have a stripe and mirror vdev in special)

Running TrueNAS Scale 22.12.3.3

Pool info:

Code:
pool: vader state: ONLINE scan: resilvered 1.13M in 00:00:01 with 0 errors on Tue Aug 15 20:39:11 2023 config: NAME STATE READ WRITE CKSUM vader ONLINE 0 0 0 raidz2-0 ONLINE 0 0 0 78aefec9-a81b-11ea-82bb-0026b942e0cc ONLINE 0 0 0 79659516-a81b-11ea-82bb-0026b942e0cc ONLINE 0 0 0 797c9eda-a81b-11ea-82bb-0026b942e0cc ONLINE 0 0 0 7993ff4a-a81b-11ea-82bb-0026b942e0cc ONLINE 0 0 0 799d506a-a81b-11ea-82bb-0026b942e0cc ONLINE 0 0 0 79a1ba46-a81b-11ea-82bb-0026b942e0cc ONLINE 0 0 0 raidz2-2 ONLINE 0 0 0 c5e2f423-3f25-4c96-9b52-58b15a19fb19 ONLINE 0 0 0 e0f272df-3ea9-4d17-935c-1ca87e66e5f6 ONLINE 0 0 0 3d36552f-a468-429b-860d-17911500f799 ONLINE 0 0 0 0d0d5fa5-047a-4fb3-8be3-f8fc8764cd83 ONLINE 0 0 0 e6d6e5ca-ec70-47cd-b582-71f9804b1a8a ONLINE 0 0 0 2a93a080-140e-4817-830c-f290d1ecc932 ONLINE 0 0 0 special f2a9eeab-3581-489c-8094-d038114901ab ONLINE 0 0 0 errors: No known data errors

This setup scares me. You have RaidZ2 on your data vdevs, which allows the loss of any two drives per vdev but your special vdev only uses a mirror. Losing two drives on this vdev destroys your entire pool. When you offlined one drive you had no redundancy in this vdev and then were considering offlining the only remaining drive keeping the pool alive

Arwen · Jan 23, 2024

sretalla said:
kuruption said:

I didn't like the "extend" button because it infers... a stripe or jbod kind of addition

Click to expand...

Well, as I said, that's the button that gets you the wanted result.

I have a bunch of older threads where I mention that Extend should not be the wording used for that button, it should say Attach.

I never got around to raising a request to have it changed.

We've got you covered;

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But, everyone Vote for it. After logging in, the Vote button is the blue, (at least for me), thumbs up in the upper right corner, (but below the header bar). Anyone with an account can Vote. And anyone can create a Jira account. Let's shoot for the most voted for change! I want a thousand Votes! (Or at least a hundred...)

This way we can express our desire for clearer instructions.

Ignoring my hyperbole, this specific "Extend" instead of "Attach a Mirror" is one of the most confusing items that creates forum posts asking how to attach a mirror. If the goal is to push new users to create a Forum account to ask that question, it succeeded.

Important Announcement for the TrueNAS Community.

Re-create special vdev mirror

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