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lvm storage: improve wording for snapshot-as-volume-chain option

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Suggested-by: Friedrich Weber <f.weber@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
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Thomas Lamprecht
2025-07-18 08:44:23 +02:00
parent 260a3738dc
commit 95871caa29
1 changed files with 10 additions and 4 deletions
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14
pve-storage-lvm.adoc
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@@ -51,8 +51,13 @@ Wipe throughput (`cstream -t` parameter value).
`snapshot-as-volume-chain`::
Set this flag to enable snapshot support for virtual machines on LVM with a
volume backing chain that uses separate volumes for snapshot virtual disk
states.
volume backing chain.
With this setting, taking a snapshot persists the current virtual disk state to
a separate volume. 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.
+
This design avoids issues with native LVM snapshots, such as significant
input/output (I/O) penalties and unexpected, dangerous behavior when running out
@@ -63,8 +68,9 @@ storage system that supports block storage. This includes iSCSI and fiber
channel-attached SANs.
+
Note that, although this feature relies on qcow2, it only uses qcow2's ability
to layer multiple volumes in a backing chain. The snapshot functionality itself
is managed by the PVE storage system, not qcow2 directly.
to layer multiple volumes in a backing chain, not qcow2's snapshot
functionality.
The snapshot functionality is managed by the PVE storage system.
+
Enabling or disabling this flag only affects newly created virtual disk volumes.