feat: Add Longhorn V2 Data Engine #653
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docs/advanced/longhorn-v2.md
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| If you wish to selectively disable the Longhorn V2 data engine on some nodes (for example on nodes with less CPU and/or RAM), go to the **Hosts** screen and add the label `node.longhorn.io/disable-v2-data-engine` with value `true` to those nodes. | ||
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| 2. Go to the **Hosts** screen and add extra disks to each node as described in [Multi-disk Management](../host/host.md#multi-disk-management). Set the additional disk's `Provisioner` to `Longhorn V2 (CSI)`. |
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We can also add some screenshots in the multidisk management page for LVM/v2 volumes.
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@tserong The structure looks good. I suggested wording improvements and dropped some comments below the suggestions. I'll answer your questions after I've had time to step back and revisit the content with fresher eyes.
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Here are my answers:
No. The "Experimental" label and how the Limitations section is worded already imply that the feature set is incomplete.
Such details could be useful. We can probably reuse some content from this section of the doc.
This section leans heavily on other doc topics (Multi-disk Management, Creating a StorageClass). Linking is the correct approach. We just need to ensure that those topics actually contain the information that the user needs.
We can add an intro paragraph to "Using the Longhorn V2 Data Engine" that contains these details. We can also convert the related paragraph in the "Limitations" section to an "Important" note. |
tserong
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Thanks @jillian-maroket, I've updated this now to include all your feedback, which I've squashed into the first commit. I've also added two other commits, one to make important info boxes, and the second to add a note about an obscure issue with disk size. I'm not 100% sure if this is the best place to put it, because the issue only occurs when testing with non-NVMe disks, and we already said that local NVMe disks are a requirement (it probably really belongs in the Longhorn docs - see my comments in the commit message at 314ff94) |
Related issue: harvester/harvester#5274 Signed-off-by: Tim Serong <tserong@suse.com> Co-authored-by: Jillian <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Tim Serong <tserong@suse.com>
This one is a little obscure. When testing with non-NVMe disks, Longhorn uses the aio bdev driver, which assumes the block size is 4096 bytes, and thus requires the disk to be an even multiple of that figure. We hit this in testing as described in harvester/harvester#6861. Ordinarily one should be using NVMe disks, which end up using the nvme bdev driver, which picks up the actual block size of the underlying device and everything just works. This subtlety (nvme bdev driver working regardless of disk size, but aio bdev driver requiring 4096 byte blocks) is apparently not documented anywhere else (e.g. it's not mentioned in the Longhorn docs) which is why I'm adding it here, just in case anyone else hits it and gets confused. Signed-off-by: Tim Serong <tserong@suse.com>
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(I missed the "Technical Preview" -> "Experimental" change in the settings page yesterday :-/) |
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Thanks, @tserong. I made a few edits to the note you added but the doc looks fab. Should be good to go soon.
Co-authored-by: Jillian <67180770+jillian-maroket@users.noreply.github.com>
This adds a new page under Advanced describing how to enable the Longhorn v2 Data Engine, along with its prerequisites and current limitations.
A couple of questions:
(We should also update the screenshots and description on the Multi-Disk Management page, but this also probably needs to include information about @Vicente-Cheng's LVM work, so I haven't included that as part of this PR.)
Related issue: harvester/harvester#5274