"Pull" a backup from a remotely mounted disk?

[DrDan in MA]

OK, a "followup question" as they say. If I want to use a local copy of SD! to do a daily-at-4AM backup of my local disk on Mac "P" to Partition "A" of my ext HD, I can use the Energy Saver PrefPane on my local Mac to wake it from sleep at 3:59 every day, and all is well.

Now, from Mac "Q" elsewhere on the LAN, I want to use another SD! to push a backup of "Q"'s disk (as a sparse image) to Partition "B" on Mac "P". I want to make that a daily affair, to happen, say, at 1AM - so that it'll be done in time for Mac "P"'s own backup to Partion "A". To do this, I can use Mac "Q"'s Energy Saver PrefPane to waken it at 12:59AM every day.

Here's the thing though: I don't think there's a way to waken Mac "P" more than once per day. And I've found that if Mac "P" is asleep when Mac "Q" (which had previously mounted Partition "B" over the network) comes a-callling, why then Mac "Q" will simply beachball.

So [unless I'm wrong ( ) on this can't-wake-a-Mac-twice-in-one-day thing?] I don't think that it will be possible to do a daily backup of both Macs, unless

1. I do one of the backups during the day, when I'm working on Mac "P" and it's awake, or
   
2. I create staggered (alternate-day) backups, one on each machine.

Viz.,

1. Have Mac "P" back itself up (via Smart Update) using its local copy of SD! to Partition "A" (hardwired to Mac "P"'s own Ext HD firewire) on Sunday, Tuesday, Thursday & Saturday at 4AM, when Mac "P" will have been set to wake daily from its slumber at 03:59, and then set things up elsewhere on my LAN such that I will also...
   
2. Have Mac "Q" back itself up using its local copy of SD! to a sparse image on Partition "B" (mounted over the network on Mac "P"'s ext HD) on Monday, Wednesday, & Friday at 4AM, when Mac "P" will have wakened from its slumber at its usual time of 03:59. Furthermore, Mac "Q" will be scheduled to wake from ITS slumber at the same 03:59, so that its local copy of SD! can in fact do its scheduled backup-over-the-network at 4AM.

So I'd have backups that could be a max of 2 days behind, rather than one day.

Oh, there's another way forward I guess: Buy a second ext HD and hard-wire it to Mac "Q". That way I could have daily backups made on both Macs.

Any of this make sense? Wrong? Better ways to accomplish? Sound like a plan? and so forth