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KB: Clarify the impacted version of filesystem trim #63

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KB: Clarify the impacted version of filesystem trim #63

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19 changes: 14 additions & 5 deletions kb/2024-01-30/the_potential_risk_with_fstrim.md
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Original file line number Diff line number Diff line change
@@ -11,16 +11,25 @@ tags: [harvester, rancher integration, longhorn, filesystem trim]
hide_table_of_contents: false
---

:::note
This issue is already resolved by Longhorn v1.5.4, v1.6.1, v1.7.0 and later versions.
:::


Filesystem trim is a common way to release unused space in a filesystem. However, this operation is known to cause IO errors when used with Longhorn volumes that are rebuilding. For more information about the errors, see the following issues:

- Harvester: [Issue 4793](https://github.com/harvester/harvester/issues/4739)
- Longhorn: [Issue 7103](https://github.com/longhorn/longhorn/issues/7103)

:::info important

Filesystem trim was introduced in Longhorn v1.4.0 because of [Issue 836](https://github.com/longhorn/longhorn/issues/836).

Longhorn volumes affected by the mentioned IO errors can disrupt operations in Harvester VMs that use those volumes. If you are using any of the following Harvester versions, see the instructions for risk mitigation in this article.

| Affected Harvester Version | Built-In Longhorn Version |
|----------------------------|---------------------------|
| v1.2.0 | v1.4.3 |
| v1.2.1 | v1.4.3 |
| v1.3.0 | v1.6.0 |

:::

## Risks Associated with Filesystem Trim

A consequence of the IO errors caused by filesystem trim is that VMs using affected Longhorn volumes become stuck. Imagine the VM is running critical applications, then becomes unavailable. This is significant because Harvester typically uses Longhorn volumes as VM disks. The IO errors will cause VMs to flap between running and paused states until volume rebuilding is completed.