[Bug 1590740] Re: grub-pc, grub2 doesn't check /dev/disk/by-id or "by-path" for zfs zpool

[brian mullan]

added some updated info.

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to grub in Ubuntu.
https://bugs.launchpad.net/bugs/1590740

Title:
  grub-pc, grub2 doesn't check /dev/disk/by-id or "by-path" for zfs
  zpool

Status in grub package in Ubuntu:
  New

Bug description:
  When creating an Ubuntu 16.04 root install on a zfs using disks & zfs
  pool created using "/dev/disk/by-id" and I get to the point of
  running:

            apt install grub-pc

  I select the 4 disks I am putting into the ZFS pool to have grub
  installed into but grub-pc fails (see attached screen shot):

  Note:  first problem is that "menu" presented by grub-pc lists them as

  /dev/sda
  /dev/sdb
  /dev/sdc
  /dev/sdd

  I think they should be listed as their "by-id" or "by-path" ... if you
  created the zfs disks and pool with that!

  In my case the disks were created/partitioned using:

  sgdisk -Z -n9:-8M:0 -t9:bf07 -c9:Reserved -n2:-8M:0 -t2:ef02 -c2:GRUB -n1:0:0 -t1:bf01 -c1:ZFS \
          /dev/disk/by-id/ata-ST2000DM001-1CH164_W1E8JLV9

  sgdisk -Z -n9:-8M:0 -t9:bf07 -c9:Reserved -n2:-8M:0 -t2:ef02 -c2:GRUB -n1:0:0 -t1:bf01 -c1:ZFS \
          /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E0713E

  sgdisk -Z -n9:-8M:0 -t9:bf07 -c9:Reserved -n2:-8M:0 -t2:ef02 -c2:GRUB -n1:0:0 -t1:bf01 -c1:ZFS \
          /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E084AP

  sgdisk -Z -n9:-8M:0 -t9:bf07 -c9:Reserved -n2:-8M:0 -t2:ef02 -c2:GRUB -n1:0:0 -t1:bf01 -c1:ZFS \
          /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E06YPY

  
  later I use this command to created the ZFS Pool of 2 mirrors each with 2 HDs using "by-id".

  zpool create -o ashift=12 -O atime=off -O canmount=off -O compression=lz4 \
       -O normalization=formD -O mountpoint=/ -R /mnt rpool mirror \
       /dev/disk/by-id/ata-ST2000DM001-1CH164_W1E8JLV9-part1 \
       /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E0713E-part1 \
       mirror /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E084AP-part1 \
       /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E06YPY-part1 -f

  And confirm the ZFS pool is created correctly by:

        zpool status

  which DOES and the above shows the disks "by-id" and NOT as sda, sdb,
  sdc, sdd

  But later in the process when running "apt install grub-pc" the disks
  are listed as /dev/sda, /dev/sdb etc.

  The grub-pc "form" where you select where to install should probably
  look something like if the disks were created "by-id":

       [ ]   /dev/disk/by-id/ata-ST2000DM001-1CH164_W1E8JLV9
       [ ]   /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E0713E
       [ ]   /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E084AP
       [ ]   /dev/disk/by-id/ata-ST2000DM001-9YN164_Z1E06YPY

  
  I did find a thread online where there is/was alot of discussion about this problem!

       https://github.com/zfsonlinux/grub/issues/5

  Some work-arounds were suggested but also some where discussing the
  root cause.

  I think in 16.04 this Grub problem still exists.

  
  My reasoning is that despite how I created the disks & the pool when I ran "apt install grub-pc" it lists the choices as /dev/sda, /dev/sdb etc.   

  And if I just go ahead and select those disks (I figured why not try
  and see what happens right?) then I get the errors shown in the
  attached screen shot.

  This "may" be a zfsonlinux BUG but since Ubuntu is now supporting ZFS
  I figured I'd report it here so others encountering it know what is
  going on.

  Lastly...

  I would suggest that the current Ubuntu Documentation on this is
  incorrect:

  https://wiki.ubuntu.com/Kernel/Reference/ZFS

  The Ubuntu ZFS documentation says:

  ZFS Pools

  A zpool is a pool of storage made from a collection of VDEVS. One or
  more ZFS file systems can be created from a ZFS pool.

  In the following example, a pool named "pool-test" is created from 3
  physical drives:

  $ sudo zpool create pool-test /dev/sdb /dev/sdc /dev/sdd

  Striping is performed dynamically, so this creates a zero redundancy
  RAID-0 pool.

  Notice: If you are managing many devices, it can be easy to confuse
  them, so you should probably prefer /dev/disk/by-id/ names, which
  often use serial numbers of drives. The examples here should not
  suggest that 'sd_' names are preferred. They merely make examples
  herein easier to read.

  
  THE ABOVE Notice I think is inaccurate in suggesting "you should probably prefer"... from all the documentation and examples I have found including the official example for installing

  Ubuntu 16.04 Root on ZFS:
  https://github.com/zfsonlinux/zfs/wiki/Ubuntu%2016.04%20Root%20on%20ZFS

  Where in "2.2 Partition your disk" it says:

  "Always use the long /dev/disk/by-id/* aliases with ZFS. Using the /dev/sd* device nodes 
  directly can cause sporadic import failures, especially on systems that have more than one storage pool."

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/grub/+bug/1590740/+subscriptions