ZFS root pool cannot be mirrored

[tigloo]

I created a ZFS root pool using a single whole disk. After the installation, I wanted to attach a second drive to the pool to create a mirrored root pool. In the first attempt, ZFS detected the disk and said it does not contain an EFI label but may contain data. Overriding with -f caused ZFS to complain that an EFI label was present.

Workaround: manually creating the same partition layout on the second drive that ZFS created on the first drive, then attaching the data partition instead of the whole drive successfully creates a mirrored pool.

till@tricky:~$ sudo zpool attach rpool /dev/disk/by-id/scsi-SATA_SAMSUNG_HD501LJS0MUJ1EQ159603 /dev/disk/by-id/scsi-SATA_SAMSUNG_HD501LJS0MUJ1EQ159604 
invalid vdev specification
use '-f' to override the following errors:
/dev/disk/by-id/scsi-SATA_SAMSUNG_HD501LJS0MUJ1EQ159604 does not contain an EFI label but it may contain partition
information in the MBR.
till@tricky:~$ sudo zpool attach rpool -f /dev/disk/by-id/scsi-SATA_SAMSUNG_HD501LJS0MUJ1EQ159603 /dev/disk/by-id/scsi-SATA_SAMSUNG_HD501LJS0MUJ1EQ159604  
cannot label 'sdb': EFI labeled devices are not supported on root pools.
till@tricky:~$

[behlendorf]

@tigloo This is a check we should just be able to disable for Linux. I'm not aware of any good reason why we can't use EFI labeled devices for the root pool. Give the following patch a try and let me know if you see any issues. This change 77a49f1784351898d7475d4b9ede9a499994821f disables all the checks which limit the use of EFI labels on root devices.

[tigloo]

Thanks for the quick patch! I'll need a few days to test it because I need to set up a new virtual machine. Should be able to do that during the weekend.

[cwedgwood]

to state the obvious (perhaps) mirroring the root pool won't make the system robust on reboot if a device fails, the boot-loader has to be updated on all mirrored devices

[behlendorf]

@tigloo Why did you close the issue?

[tigloo]

Oops, sorry. Meant to add a comment, then decided otherwise. Instead of discarding the comment, I accidentally pressed the close button. Re-opening.