Can selected drives hang up timecapsule?

Question

I have a White Macbook (Early 2008) running OSX 10.7.5 that has been having crashing and shutdown problems lately. I am wondering if it has to do with source drives being backed up and/or destination drives. Let me explain:
Source drives: I have one Maxtor 320GB extrenal drive attached to the Macbook via USB through a hub. This is selected to be backed up along with the main internal hard drive.
Desintation drives: I am running TimeMachine for backup through an Apple 1TB TimeCapsule/Wifi Router using a WiFi network connection (FYI: this Time Capsule and one USB-connected 1TB drive are at capacity backing up two other Macs on this network). Connected to that TimeCapsule/Router via ethernet hardwire is an iMac which has an external dual drive bay attached to it via USB. One 2TB drive is used for work on that iMac, the other 2TB is partitioned into 1TB "drives" and one of these is being used as an auxillary backup drive. It is this latter drive that the White Macbook is backing up to.
The problem I am having is a shutdown problem, occuring most often along with program crashes (which has also been happening with increasing frequency - mainy Picasa but also Firefox, iTunes and others). Whether a program on the machine crashes or not upon Shutdown, the OS will sometimes hang up on the desktop with the rainbow wheel spinning interminably. This often happens when the the Macbook is shutdown while a Backup is running. In this case, the Macbook simply never reaches a shutdown point. It can run all night and all day in this state. What also often happens is that the Macbook will go through the whole shutdown process right up to the point where it reaches a white screen. It will stop at this point and not progress any further - this white screen will also stay on interminably.
The only way to finish shutdown or in fact to interrupt these processes in any way is a forced power-off by holding down the Macbook's power button.
I took it to the Genius bar and they just wiped the hard drive and did a fresh OS install. It went OK like this for a few days, but eventually these crashing and non-shutdown problems recurred.
Does anyone have any idea if it might be the backup confuguration causing this, or somethign else?

Answer 1

You know, when I had a car (I don't drive anymore, just walk and bike now), I would occasionally not drive it for a day or two (not very often, though). It would take a moment longer to start up after that. Ever left a car out in the ice cold for a week? Be careful starting that baby up.
It's not a very good analogy, and most of the mechanics don't apply, but shutting down and starting up an HDD puts some "wear and tear" on the device as well. In fact, since an HDD is designed to spin rapidly and run for indefinite periods of time, by leaving it on all the time, you are doing what the HDD is designed to do. They are clearly not optimized for spin-down / spin-up cycles, because this significantly slows down the system, and has been known to cause temporary "freezes" in the OS.
Seriously, turning your HDD off as often as possible won't necessarily extend its life, and may even shorten it, depending on how you use it. As has been mentioned, many systems run for months at a time without shutting down, especially servers. No server can afford to spin-down it's HDDs during periods of inactivity (if there were such a thing for a server), because it then cannot perform its job.
Take it easy, and let your HDD do its thing. Let it spin-down at the most natural time for an HDD: when you shut your computer off. Other than that, I recommend letting it go all the time. Though there is something to be said for that little bit of electricity that is saved, and therefore prevents another polar bear from having to float away on a chunk of ice.
Seriously, though, energy conversation is awesome, and if that is your reasoning, I totally support that. But the argument from the life of the HDD is mostly moot.