Time Machine Behavior

[nkhester]

I have 2 external FireWire drives. One serves exclusively as Time Machine. The other is divided into two equal partitions: one contains a full SD! backup; the other contains an SD! Sandbox.

Normally I would expect that the Time Machine would perform its scheduled updates only from Macintosh HD. This morning I noticed long activity by Time Machine while booted from the Sandbox. Later when I rebooted from Macintosh HD, I found that Time Machine had essentially doubled in size!

Does Time Machine attempt to backup from attached peripherals? I have assumed "no" --- but I may be wrong!

But, something peculiar was going on with Time Machine when I was surfing from the Sandbox...

I've subsequently rebooted from the Sandbox and did not notice any strange Time Machine behavior (because a second "full" backup was achieved on my last visit?).

Does anyone have any idea what may have happened --- or, any suggestion for prudent action on my part?

MY system configuration is:

Computer Model: iMac 24/2.8/2GB/500GB/SD
Operating System: Mac OS X (10.5.2)
Other Info: HP C7280, WD MyBook x 2, SuperDuper!, APC RS1500

nkhester