Skip to content

docs(lvm-local-storage): considerations for striped vs dm-thin#1075

Open
abonillabeeche wants to merge 9 commits into
harvester:mainfrom
abonillabeeche:docs-lvm-considerations
Open

docs(lvm-local-storage): considerations for striped vs dm-thin#1075
abonillabeeche wants to merge 9 commits into
harvester:mainfrom
abonillabeeche:docs-lvm-considerations

Conversation

@abonillabeeche

Copy link
Copy Markdown
Contributor

Summary

Adds two small pieces to the LVM Local Storage add-on documentation:

  1. A brief Considerations: striped vs dm-thin section right after the StorageClass creation step, to help operators pick the right volume group type at the moment they are configuring it.
  2. A small Additional Notes section at the bottom, covering:
    • Tuning knobs on the dm-thin pool (chunk zeroing, metadata size).
    • Recommendation to use virtio-scsi for VM disks backed by LVM CSI.
    • Coexistence with Longhorn v2 block-mode disks (LVM global_filter).

Same content is applied to both:

  • docs/advanced/addons/lvm-local-storage.md (main)
  • versioned_docs/version-v1.8/advanced/addons/lvm-local-storage.md (v1.8)

Motivation

Both volume group types are already listed as supported, but the doc doesn't currently guide the reader on when to pick one over the other. In particular, the fact that striped snapshots reserve the origin's full capacity at creation time (versus dm-thin snapshots being effectively free at creation) is important for anyone planning to take regular snapshots on their VM workloads.

The Longhorn v2 coexistence note references harvester/harvester#11098 for background.

Notes

Documentation-only. No behavior changes.

Add a brief comparison of the two volume group types to help operators
pick the right StorageClass for their workload, and append a small
"Additional Notes" section covering thin-pool tuning, VM disk-bus
recommendation, and Longhorn v2 coexistence.

Signed-off-by: Alejandro Bonilla <abonilla@suse.com>

@jillian-maroket jillian-maroket left a comment

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Review done

Comment thread docs/advanced/addons/lvm-local-storage.md Outdated
Comment on lines +107 to +116
### Considerations: `striped` vs `dm-thin`

Both volume group types are fully supported. The choice depends on how the workload will use snapshots and how the pool capacity will be shared.

- **`striped`** is a good fit for workloads that mostly need direct volume performance across the physical devices in the volume group. Each logical volume gets its full requested capacity at provision time. Snapshots are provisioned as separate LVs sized to the origin's full capacity — a snapshot of a 100 GiB volume reserves an additional 100 GiB of volume group space at creation, regardless of how much data has actually been written to the origin.

- **`dm-thin`** is a good fit for virtual machine workloads that take snapshots or clones, and for environments that want to over-provision pool capacity. Thin volumes consume physical space only as blocks are written to them, and snapshots are true copy-on-write at the thin-pool chunk level — a fresh snapshot of a 100 GiB volume adds effectively zero pool capacity at creation and only grows as changed blocks accumulate.

If regular snapshots are expected, `dm-thin` is generally the right choice for VM workloads.

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I moved the text to the procedure above. Please remove these lines.

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done in commit c36d7d7 — removed the ### Considerations: striped vs dm-thin section (now redundant with your rewritten Volume Group Type step above). Kept the trailing For more information, see [StorageClass] link as a standalone pointer. Signed off with a Co-authored-by: trailer for you since the guidance came from your review.

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Please verify!

Comment thread docs/advanced/addons/lvm-local-storage.md Outdated
Comment thread docs/advanced/addons/lvm-local-storage.md Outdated
Comment thread docs/advanced/addons/lvm-local-storage.md Outdated
Comment thread docs/advanced/addons/lvm-local-storage.md Outdated
Comment thread docs/advanced/addons/lvm-local-storage.md Outdated
Comment thread docs/advanced/addons/lvm-local-storage.md Outdated
abonillabeeche and others added 8 commits July 13, 2026 10:27
Co-authored-by: Jillian Maroket <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Alejandro Bonilla <abonilla@suse.com>
Co-authored-by: Jillian Maroket <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Alejandro Bonilla <abonilla@suse.com>
Co-authored-by: Jillian Maroket <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Alejandro Bonilla <abonilla@suse.com>
Co-authored-by: Jillian Maroket <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Alejandro Bonilla <abonilla@suse.com>
Co-authored-by: Jillian Maroket <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Alejandro Bonilla <abonilla@suse.com>
Co-authored-by: Jillian Maroket <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Alejandro Bonilla <abonilla@suse.com>
Co-authored-by: Jillian Maroket <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Alejandro Bonilla <abonilla@suse.com>
Jillian moved the striped vs dm-thin explanation into the procedure step
above (Volume Group Type), so the standalone section is now duplicate
content. The "For more information, see [StorageClass]" link is kept.

Co-authored-by: Jillian Maroket <67180770+jillian-maroket@users.noreply.github.com>
Signed-off-by: Alejandro Bonilla <abonilla@suse.com>

@jillian-maroket jillian-maroket left a comment

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

LGTM. Thanks!

@mergify

mergify Bot commented Jul 14, 2026

Copy link
Copy Markdown

Tick the box to add this pull request to the merge queue (same as @mergifyio queue).

  • Queue this pull request

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Labels

None yet

Projects

None yet

Development

Successfully merging this pull request may close these issues.

2 participants