From a4ad4f48b97cd0334a1d1483815a1c0c4a6fbed3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Fabian=20Gr=C3=BCnbichler?= Date: Fri, 25 Jul 2025 11:52:08 +0200 Subject: [PATCH] lvm: add note about requirements of snapshot-as-volume-chains MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Fabian Grünbichler Link: https://lore.proxmox.com/20250725095208.249266-1-f.gruenbichler@proxmox.com --- pve-storage-lvm.adoc | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/pve-storage-lvm.adoc b/pve-storage-lvm.adoc index 6928330..c508fe1 100644 --- a/pve-storage-lvm.adoc +++ b/pve-storage-lvm.adoc @@ -57,8 +57,7 @@ snapshot's name and starts a new volume backed by the snapshot. + A volume based on a snapshot references its parent snapshot volume as its backing volume and records only the differences to that backing volume. -Snapshot volumes are currently thick-provisioned LVM logical volumes, but the -underlying block storage may provide thin provisioning. +Snapshot volumes are currently thick-provisioned LVM logical volumes. + This design avoids issues with native LVM snapshots, such as significant input/output (I/O) penalties and unexpected, dangerous behavior when running out @@ -74,6 +73,11 @@ functionality. The snapshot functionality is managed by the PVE storage system. + Enabling or disabling this flag only affects newly created virtual disk volumes. ++ +For efficient support of `snapshot-as-volume-chain`, the backing storage must +support thin-provisioning and discard. Each snapshot will appear to use the +full volume size on the PVE side, but the actual space usage on the underlying +storage will be smaller if those requirements are met. .Configuration Example (`/etc/pve/storage.cfg`) ----