While I was at the hosting site adding memory to the second aprs.fi frontend today, I also did maintenance on the Sun Enterprise 4500 server which hosts finland.aprs2.net (the Tier 2 APRS-IS server which aprs.fi uses as the data source) and the aprs.fi backup database. So I configured the primary aprs.fi server to connect to another APRS-IS server while finland.aprs2.net was down, but made a mistake in the configuration, so the APRS-IS data collection broke. I didn't notice the alarms which it triggered, because I was working hard with the memory upgrade and the Sun reboot.
As a result, aprs.fi didn't collect APRS data between 11:35:43 UTC and 14:21:13 UTC. Sorry about that, I'll try to be more careful next time.
The memory upgrade itself went fine. The server should perform quite well for a while now.