From: Fiona Ebner <f.ebner@proxmox.com>
To: pve-devel@lists.proxmox.com
Subject: [pve-devel] [PATCH docs] qm: guest trim: add note mentioning issue with ext4
Date: Fri, 10 Mar 2023 10:06:48 +0100 [thread overview]
Message-ID: <20230310090648.26873-1-f.ebner@proxmox.com> (raw)
It is rather unexpected and seems worth mentioning. Reported in the
community forum [0] and the explanation found by Alwin [1].
[0]: https://forum.proxmox.com/threads/123819/
[1]: https://serverfault.com/questions/1113127/fstrim-is-very-slow-on-xfs-and-always-return-same-value-unlike-ext4/1113129#1113129
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
qm.adoc | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/qm.adoc b/qm.adoc
index bd535a2..3ba2a3c 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -1063,6 +1063,12 @@ operations that have the potential to write out zeros to the storage:
On a thin provisioned storage, this can help to free up unused space.
+NOTE: There is a caveat with ext4 on Linux, because it uses an in-memory
+optimization to avoid issuing duplicate TRIM requests. Since the guest doesn't
+know about the change in the underlying storage, only the first guest-trim will
+run as expected. Subsequent ones, until the next reboot, will only consider
+parts of the filesystem that changed since then.
+
Troubleshooting
^^^^^^^^^^^^^^^
--
2.30.2
next reply other threads:[~2023-03-10 9:07 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-10 9:06 Fiona Ebner [this message]
2023-03-10 9:43 ` Laurent GUERBY
2023-03-10 11:39 ` Fiona Ebner
2023-03-11 16:58 ` [pve-devel] applied: " Thomas Lamprecht
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