We typically only do maintenance once every couple of months and only to one or two servers at a time, but this weekend will be pretty ridiculous.
The database servers listed below will halt traffic processing for up to 10 hours this weekend while we perform some necessary maintenance, starting either Friday night (if I get it ready in time), or Saturday morning. (This is US pacific time, GMT -7). When the maintenance is done, they will all have a large backlog of traffic to process before they are caught up with real time again.
(Spy will still working during this time, because it is an actual live stream of data as it comes into our tracking servers, rather than using the database. So if you have a paid account you can still keep up with basic stats via Spy during the maintenance.)
These are mostly older servers so most sites registered within the last year or so should be unaffected. The exceptions are db27 and db33 which are less than a year old. These servers have quite a bit less data than the other ones though so their maintenance window should be quite a bit shorter.
To determine which database server a site is hosted on, take a look at the preferences page for that site.
Affected database servers:
1 – 11, 15, 17, 18, 20, 21, 23, 27, 33