I requested the R20210426-P2
update on a Monday and it was completed on the next Saturday so roughly 6 days from request to actual update. It's also worth noting that the update does not show up in the Upgrade
tab in the UI, it shows up in the Notifications
tab with this:
Service software update R20210426-P2 completed.
[UPDATE 11 Jul 2021] I just proceeded with updates on two additional domains and the updates began within 15 minutes.
[UPDATE 17 Dec 2021 Log4J CVE] I've had variable luck with the R20211203-P2. One cluster updated in a few hours and one took a few days. A third I was sure I started a few days ago but it gave me the option to update today (possibly a timeout?). I'm guessing they limit the number of concurrent updates and things are backed up. I recommend continuing to check the console but have patience, they do eventually get updated. If you have paid support, definitely open a ticket.