[ovirt-devel] Re: Change compatibility level for data center/cluster during upgrade - what exactly are we changing?
On Mon, Nov 9, 2020 at 11:18 AM Patrick Chiang <patrick(a)yun.to> wrote:
Hi all,
From the upgrade procedure, when we completed most upgrade tasks, we have to change the
compatibility level in cluster and data center, and then restart all guest VM
afterwards.It seems no down time expected with these 2 changes from the procedure.
What kind of upgrade? 4.3.x to 4.3.y? or 4.3.x to 4.4.y?
I wonder what exactly we are changing (a setting in the
database/file??)
The version in the engine database. Based on this version, new APIs can be
used exposing new features.
On the host side, using a new version may allow the upgrade of storage domains
to a new version, again providing new features.
and most important of all, whether there will be a few seconds down
time when we made those changes to "data center"?
Changing cluster compatibility level should not cause any downtime
for running vms.
On the SPM side, this may cause an upgrade of all storage domains from
version x to version y. This may cause delays in some tasks since the storage
domain and the SPM is locked during the upgrade, but it should not be visible
to users normally.
Because I worried if a data center change could lead to storage
domain's down time and eventually force hypervisors, guest VM restart before expected
time. (My hosts/guest VM directly use HP 3par's storage as boot disks/data disks...)
I don't expect any special trouble when changing cluster compatibility level.
Nir