Support for multiple storage.

[khfeng]

There are several different combinations, notably:

• 1 SSD + 1 HDD

• 2 HDDs

• 2 SSDs

Current dell-recovery only uses one storage device, but having LVM RAID, btrfs, zfs can be really helpful on combinations above.

[superm1]

Stage 1 of dell-recovery emulates the conditions that happen in Dell factory process earlier before Ubuntu install kicks off. Coming into stage 2 Ubiquity will use the largest free space to format (https://github.com/dell/dell-recovery/blob/master/casper/seeds/ubuntu.seed#L74)
and will follow this recipe:
(https://github.com/dell/dell-recovery/blob/master/casper/seeds/ubuntu.seed#L81)

So I think the first thing that is really needed is support for a way to tell Ubiquity to use the free space across all the disks. Once that is possible, then the defaults recipe in dell-recovery can be changed to generate an LVM partition in the free space of the first disk and all the space of the second disk.

Can that be discussed with Ubuntu foundations folks?

[khfeng]

I think you are right, this should be integrated into ubiquity.
I'll see what I can do to it =)

[superm1]

@khfeng thanks. Keep me and @kevinkellyspacey looped in as that work happens. I'm hoping that dell-recovery can just change ubuntu.seed for supporting this recipe and call out the disks to participate when this recipe is used (such as how we "dynamically" fill in what disk to install to today).

Once ubiquity is ready in an intermediary Ubuntu release with this feature, we'll pick this bug up.

[khfeng]

After some digging on partman, I now understand what you really mean in comment 2.

What requires here is Ubiquity needs to ask partman-auto to do partitioning on multiple storages, override partman's default fs (EXT4), then ask partman-{lvm|btrfs|zfs} to do the rest.

More importantly, Ubuntu will use UbuntuImage [1] to build classic image in the future, so we should check out how preseed works, how it cooperates with Ubiquity.

[1] https://wiki.ubuntu.com/UbuntuImage

[superm1]

I wasn't aware that Ubuntu image building would move to that, but I don't think it should change much about how images are used for dell-recovery since dell-recovery does actively use preseeding already. Was there something particular about how it's being with UbuntuImage now that you think will break?

[khfeng]

My understanding is the preseeding uses debian-installer heavily, I don't think the new ubuntu-image will use d-i at all. I'll ask around.

[superm1]

Oh so you are meaning that UbuntuImage based images might not take Ubiquity? That would be a very big change and yes would cause lots of problems for dell-recovery as it exists.. How soon are UbuntuImage based images for "classic" Ubuntu going to be starting to get used? I wasn't aware of this.

[superm1]

@khfeng did you ever have any results from digging into this further for partman-auto to take into account multiple storage devices? It would be nice if this could be targeted for next Ubuntu LTS.

[khfeng]

Not really. This TODO completely slipped through.

Looks like the plan forward is to use LVM - do we use the SSD as root partition or a cache layer?

[khfeng]

There's already a blog [1] explains how to use preseed to do multi-disks partitioning.
If the partition schemes it supported are what we want, it shouldn't be too hard to integrate into dell-recovery.

[1] https://www.claudioborges.org/?p=733

[superm1]

Thanks for sharing that link. Yes, in general LVM should be the path forward. It should allow the most flexibility across multiple disks,.

It would be great to expose the SSD as cache (using LVM's cache features eg: https://rwmj.wordpress.com/2014/05/22/using-lvms-new-cache-feature/) but I don't know that partman will be able to expose this level of detail.

So I see this should be broken up into a few milestones. I've created a wiki that we can track progress here:
https://github.com/dell/dell-recovery/wiki/Multiple-disk-support