From de110b042d8e340d19a52b9fb7ef6f4c52bc0762 Mon Sep 17 00:00:00 2001 From: Pedro Almeida Date: Tue, 8 Feb 2022 14:51:46 -0300 Subject: [PATCH] Update live_migration_downtime definition Before, the definition of live_migration_downtime didn't explain if any exception/timeout occurs if the migration exceeds the value. This is just used as a reference for nova and if any problem happens when the VM gets paused, there will be no abort or force-complete. Closes-Bug: #1960345 Signed-off-by: Pedro Almeida Change-Id: I336481d1801a367b5628fedcd2aa5f5cf763355a --- doc/source/admin/configuring-migrations.rst | 6 ++++-- nova/conf/libvirt.py | 7 ++++--- 2 files changed, 8 insertions(+), 5 deletions(-) diff --git a/doc/source/admin/configuring-migrations.rst b/doc/source/admin/configuring-migrations.rst index 4de7fe36aa5f..357189b3b18d 100644 --- a/doc/source/admin/configuring-migrations.rst +++ b/doc/source/admin/configuring-migrations.rst @@ -263,8 +263,10 @@ memory-intensive instances succeed. live_migration_downtime_steps = 10 live_migration_downtime_delay = 75 - ``live_migration_downtime`` sets the maximum permitted downtime for a live - migration, in *milliseconds*. The default is 500. + ``live_migration_downtime`` sets the target maximum period of time Nova will + try to keep the instance paused during the last part of the memory copy, in + *milliseconds*. This value may be exceeded if there is any reduction on the + transfer rate after the VM is paused. The default is 500. ``live_migration_downtime_steps`` sets the total number of adjustment steps until ``live_migration_downtime`` is reached. The default is 10 steps. diff --git a/nova/conf/libvirt.py b/nova/conf/libvirt.py index 199cc6cf5eeb..7d9c837ba569 100644 --- a/nova/conf/libvirt.py +++ b/nova/conf/libvirt.py @@ -321,13 +321,14 @@ Please refer to the libvirt documentation for further details. default=500, min=100, help=""" -Maximum permitted downtime, in milliseconds, for live migration -switchover. +Target maximum period of time Nova will try to keep the instance paused +during the last part of the memory copy, in *milliseconds*. Will be rounded up to a minimum of 100ms. You can increase this value if you want to allow live-migrations to complete faster, or avoid live-migration timeout errors by allowing the guest to be paused for -longer during the live-migration switch over. +longer during the live-migration switch over. This value may be exceeded +if there is any reduction on the transfer rate after the VM is paused. Related options: