On Mon, Nov 9, 2020 at 11:18 AM Patrick Chiang <patrick@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