chaos's questions

Note: This is a "documenting my process" question that I'll be writing an answer to. Happily, serverfault already helped me solve this, because writing up my situation so others would be able to assess it caused me to realize what was happening.

1. I'm using the ext3 filesystem on a Debian server.
2. Despite very little activity happening on my main filesystem with respect to files, there's tremendous activity from kjournald (seen via iotop).
3. This activity comes in periodic bursts that raise my overall average writes to about 2 MB/sec (which is of great concern to me because I'd like to get some SSDs and that rate is actually enough to seriously threaten the very generous write endurance of current models).
4. I've already made the filesystem in question mount with noatime,nodiratime.
5. I've already increased the filesystem's journal commit interval from 5 sec to 300 sec.

What is going on? (Spoilers: it was a userspace thing. I'm writing this mainly to highlight the possibly-counterintuitive underlying issues.)

Sometimes I hear that you shouldn't plug (UPS brand X / any UPS) into (power strip brand X / any power strip) because of some interaction leading to poorly conditioned power, reduced battery life, massive explosions spattering the room with battery acid, and so on. Sometimes I hear that it's the power strip that you shouldn't plug into the UPS. What I haven't gotten is a clear idea of how reliable these recommendations are or how generally/specifically they apply.

Can anyone speak precisely and non-urban-legendfully on these UPS and power strip interactions, if there are in fact ones worth thinking about?

So I have this going on:

# apt-get update
Get:1 http://ftp.us.debian.org etch Release.gpg [1032B]                     
Hit http://ftp.us.debian.org etch Release                                        
(...bunch more of this elided...)
Hit http://ftp.us.debian.org etch/contrib Sources
Fetched 68.8kB in 1s (37.4kB/s)
Reading package lists... Done
W: There is no public key available for the following key IDs:
9AA38DCD55BE302B
W: GPG error: http://ftp.us.debian.org etch Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9AA38DCD55BE302B
W: You may want to run apt-get update to correct these problems

Apparently I can't run apt-get update because of a problem that apt-get wants me to run apt-get update to fix, which is displeasing. How do I correct this?

Which performs better under heavy CPU and memory usage on the virtual servers, Xen or VirtualBox?