Can we add a 3rd mirror to boot-pool?

TrueNAS General
1

TrueNAS SCALE 24.10.2

Mirrored boot-pool (2-way)

I want to add a 3rd mirror but I do not see any way to do this from the UI. I know I can zpool add but that is not supported under TrueNAS.

I want to add the 3rd mirror and not replace as I want to look at the state of all 3 mirror devices after adding the 3rd mirror. I am testing a fix for https://forums.truenas.com/t/clean-install-of-24-10-0-results-in-cannot-import-boot-pool-no-such-pool-available/ that does NOT require reinstallation.

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Make sure to use zpool attach and not zpool add or you will end up with a striped pool made from a mirror and a single drive vdev.

But that should work. Copy the partition table and attach the partition, not the entire drive.

1 Like
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You are, of course, correct attach and not add, I was working from memory. Before I issue any manipulative zpool commands I review the man page :slight_smile:

I will try that and see if TrueNAS recognizes it. But it may not test what I am shooting for, since that will not partition nor write boot loader (GRUB2).

  1. I have a mirror now, call the devices A and B.
  2. I want to add C.
  3. Compare A and C.
  4. Remove A.
  5. Reinitialize A.
  6. Attach A.
  7. Repeat for B.
  8. Remove C.

And see if that clears the cannot import boot-pool problem.

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Yes, I thought you could use the native Linux partition tools and then dd(1) to copy over the GRUB partition from your current drive A.

What do you mean by “compare A and C”? You need to construct C as a copy of A as far as partitions are concerned.

If you suspect there might be something wrong, why not set a convenient maintenance window, export and save config, reinstall, import config?

The boot pool layout, GRUB and stuff are not part of the saved config. You will be getting a clean factory new boot pool and auxiliary partitions.

P.S. Just noticed the other thread.

See Clean install of 24.10.0 results in "cannot import ‘boot-pool’ : no such pool available" - #31 by pmh

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I am seeing what looks like a corrupt ZFS label on the boot-pool drive, but it is in position 2, positions 0 and 1 are empty.

Part of what I am trying to do is determine the underlying problem. In other words, what is the installer for 24.10.x failing to do correctly so I can open a detailed bug report and get it fixed.

Plus the challenge of fixing it in place.

6

Can you have all the drives in the system at the same time?

  • copy partitions manually (I have to google for Linux every time and every distro comes with different tools, so …)
  • zpool attach
  • check for presence/absence of strange artefacts on drive C
  • detach drive A
  • wipe ZFS partition with dd(1)
  • reattach drive A
  • repeat last three steps for drive B

Unless the “stuff” irritating GRUB is outside the ZFS partitions that should do it.

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Part of what I am looking for is what artifacts the TrueNAS tools create. Using the underlying ZFS tools will (probably) not show me that. But I agree that the process @pmh lays out would fix the problem.