Today I was trying to do a backup to my WHS and I was getting the message on my client:
Backup is waiting on (cleanup).
After quite a long time, it was still on this message.
I did some investigating on the server and saw that 45 minutes earlier my server had kicked off a backup cleanup process. This was indicated in the event viewer under “Homeserver”.
Task Manager also showed whsbackup.exe doing a lot of work.
So, if you run into this, just wait a bit and when the server is done with the cleanup the client backup will start like normal.