[PATCH] docs: mention migrate-setmaxdowntime's impact on snapshot-create
The migrate-setmaxdowntime command sets the max allowed downtime during live-migration, but since `snapshot-create` performs qmp migration, it also affects the downtime during internal/external snapshot creation. Resolves: https://gitlab.com/libvirt/libvirt/-/issues/593 Signed-off-by: Abhiram Tilak <atp.exp@gmail.com> --- This issue was a minor change, yet it has remained without any updates for some time. docs/manpages/virsh.rst | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst index fa038e4547..18bdae53c9 100644 --- a/docs/manpages/virsh.rst +++ b/docs/manpages/virsh.rst @@ -3717,7 +3717,8 @@ migrate-setmaxdowntime Set maximum tolerable downtime for a domain which is being live-migrated to another host. The *downtime* is a number of milliseconds the guest is allowed -to be down at the end of live migration. +to be down at the end of live migration. This is also used to set the max +downtime for creating a snapshot using ``snapshot-create``. migrate-setspeed -- 2.44.0
On Mon, May 13, 2024 at 01:36:27 +0530, Abhiram Tilak wrote:
The migrate-setmaxdowntime command sets the max allowed downtime during live-migration, but since `snapshot-create` performs qmp migration, it also affects the downtime during internal/external snapshot creation.
Resolves: https://gitlab.com/libvirt/libvirt/-/issues/593 Signed-off-by: Abhiram Tilak <atp.exp@gmail.com> --- This issue was a minor change, yet it has remained without any updates for some time.
docs/manpages/virsh.rst | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst index fa038e4547..18bdae53c9 100644 --- a/docs/manpages/virsh.rst +++ b/docs/manpages/virsh.rst @@ -3717,7 +3717,8 @@ migrate-setmaxdowntime
Set maximum tolerable downtime for a domain which is being live-migrated to another host. The *downtime* is a number of milliseconds the guest is allowed -to be down at the end of live migration. +to be down at the end of live migration. This is also used to set the max +downtime for creating a snapshot using ``snapshot-create``.
While this is true, the usefulness of setting max downtime for snapshots is questionable at best. Snapshots are mostly created in paused state when this doesn't make sense at all since the VM is "down" the whole time. During "live" snapshots (which are not used very much as the memory image will be unnecessarily large) this might apply, but generally local storage is usually fast enough for this to not be a problem. I'm not sure what this bit of documentation would provide to the user.
On Mon, 13 May 2024 at 13:38, Peter Krempa <pkrempa@redhat.com> wrote:
The migrate-setmaxdowntime command sets the max allowed downtime during live-migration, but since `snapshot-create` performs qmp migration, it also affects the downtime during internal/external snapshot creation.
Resolves: https://gitlab.com/libvirt/libvirt/-/issues/593 Signed-off-by: Abhiram Tilak <atp.exp@gmail.com> --- This issue was a minor change, yet it has remained without any updates for some time.
docs/manpages/virsh.rst | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst index fa038e4547..18bdae53c9 100644 --- a/docs/manpages/virsh.rst +++ b/docs/manpages/virsh.rst @@ -3717,7 +3717,8 @@ migrate-setmaxdowntime
Set maximum tolerable downtime for a domain which is being
On Mon, May 13, 2024 at 01:36:27 +0530, Abhiram Tilak wrote: live-migrated to
another host. The *downtime* is a number of milliseconds the guest is allowed -to be down at the end of live migration. +to be down at the end of live migration. This is also used to set the max +downtime for creating a snapshot using ``snapshot-create``.
While this is true, the usefulness of setting max downtime for snapshots is questionable at best. Snapshots are mostly created in paused state when this doesn't make sense at all since the VM is "down" the whole time.
During "live" snapshots (which are not used very much as the memory image will be unnecessarily large) this might apply, but generally local storage is usually fast enough for this to not be a problem.
I'm not sure what this bit of documentation would provide to the user.
Yeah, I also think it makes more sense to mention how the flag affects snapshot-create in the snapshot-create documentation, especially where we talk about taking live snapshots, instead of doing so under migrate-setdowntimemax's. Otherwise, this this doesn't look quite helpful. -- Abhiram
participants (3)
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Abhiram Tilak -
atp exp
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Peter Krempa