Unable to successfully boot from SAN with multipath SAS volume

[Matt Schulte]

I work at NetApp and we have a storage array that has dual SAS controllers that present multiple paths to a single volume. We usually are able to boot from SAN using SAS and utilize multipath on the root volume. I have tried everything I can think of and don't get this fully working. Here's what I have tried:

1. Installed to a single path (sda) and booted then tried to add the two paths to root into multipath.
   a. Followed https://help.ubuntu.com/lts/serverguide/multipath-setting-up-dm-multipath.html "Setting Up DM-Multipath" Could not get multipath to manage the paths.
   b. Even tried the instructions from RedHat: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/dm_multipath/move_root_to_multipath Manually adding the paths to multipath and then rebuilding the initrd, still no dice.

2. Reinstall. After many struggles I am able to install using the boot parameter: install disk-detect/multipath/enable=true
   a. Install completes but the tools are unable to write a boot loader to the multipath disk.
   b. Tried booting into a rescue disk to write bootloader and still unsuccessful.

Should Ubuntu support boot from SAN using a multipath volume on the SAS protocol (Broadcom 12G HBAs)?

[Matt Schulte (gimpyestrada)]

This has all been testing with Ubuntu 20.04. When I did have it install to a single path, I updated everything to the latest (even tried the proposed stuff) up to 3/30/2020.

When I switched tactics and tried to reinstall I was using an ISO from a couple weeks ago.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1870146/+editstatus and add the package name in the text box next to the word Package.

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[Matt Schulte (gimpyestrada)]

At this point I have to assume that booting form SAN using a SAS multipath device is not compatible with Ubuntu 20.04 and will advise against its attempted use.

[Matt Schulte (gimpyestrada)]

Anybody have anything to add here?