I’m happy to announce that first release candidate of Kopia v0.9 is finally out. It’s a big release, with lots of internal changes and some major performance improvements.
Read the release notes and download from here:
Upgrade instructions are here: Upgrade | Kopia
Some questions about the format change that I didn’t see documented anywhere.
Will this be something that migrate things slowly over time or will it require me to download and re-upload data? If it is the latter, how does it handle if the operation is aborted early (connection drops, OOM, etc)?
Upgrade is a relatively simple operation and only updates indexes which are usually small. Upgrade is also atomic - it rewrites kopia.repository blob to indicate new version is to be used.
There are no upgrade doc on the website yet, in the meantime please use this:
To upgrade repository:
kopia repository disconnect
Repository | Disconnect.This is super important, failure to do so may corrupt repository*
Upgrade all kopia executables to >=v0.9.0-rc1
Using connected kopia, run:
$ kopia repository set-parameters --upgrade
$ kopia repository status
You should see Format version: 2
After upgrade all new v0.9 features will be supported except password change. At this point kopia v0.8 will fail to open the repository.
Very exciting times! Thank you for all the hard work on this RC! I look forward to upgrade all repos.
Congratulations!
About 2 month passed since [TESTERS NEEDED] Major improvements to repository index format
Thank you very much for your hard work and time spend! 
I’m a bit confused.
- Disconnect all but one kopia clients
Can I use my Kopia Repo Server as the remaining connected instance?
- Upgrade all kopia executables
All but the one still connected?
Or should step 3. be performed using an updated kopia instance?
Can someone shed a light for me?
I’m afraid of screwing-up my repo…
Yes. You can use repo server for that but it must be stopped.
Also you need to upgrade all instances when only one is still connected including that one.