Time Machine and Time Capsule don't seem to work well together?

Question

Reposted.
I get the feeling there are some serious problems with the combination of Time Machine and Time Capsule.
This is extremely disappointing, as the idea of a centralized backup device on the network (instead of disks attached to each and every computer we have running Leopard) seemed like such a good idea and a good way to supplement our tape-based backup that takes place with Retrospect.
In reality, it's a disaster on both Intel and PowerPC systems. All systems and the Time Capsule are fully up to date with software updates from Apple. I have two 1TB Time Capsule units. It goes something like this:
1. I have a few systems (mainly Intel) that work perfectly with the Time Capsule. There are no complaints and no issues at all. These systems just quietly run their backups as they should. They are the definite minority--maybe one or two have worked properly.
2. I have some systems that complain from time to time (mainly PowerPC) but will back up with a little encouragement. These too are the minority.
3. And finally, I have systems that are nothing but pain. These are both Intel and PowerPC systems. They are also the majority of the systems I have. The most common problem is sudden loss of the credentials needed to access the Time Capsule hardware--a user will be going along about their business when the Mac OS asks for the Time Capsule user name and password--after it's already been supplied and backups have been running. This should simply never ever happen.
Another charming behavior I've seen is corruption of the sparse disk image file that each computer creates on the Time Capsule. Time Machine will complain that it can't perform the backup, and examining the disk image file with Disk Utility shows it to be severely damaged. Turning off Time Machine, deleting the corrupted sparse image file, and starting over fixes it. For a while.
Finally, there are the machines (again, both Intel and PowerPC) that just can't seem to actually get through the first backup run. They either go so far and can't continue, or never actually manage to get started. I've checked the disks in these computers and found no problem with the hardware or file system. The installations are fresh and fully up to date.
Meanwhile, I have computers running Leopard with directly attached disks configured for use with Time Machine. One is a QuickSilver that isn't even officially supported by Leopard, with a Firewire attached disk. It doesn't skip a beat. The other is an Intel Mac mini being used with Mac OS X Server 10.5.4 and a USB external hard drive. These machines just do their thing, and I never have to babysit them.
These problems with the Time Capsule have been so severe that I've just given up on most of the computers and shut off Time Machine entirely. We have tape backups that run over the week, so it's not a huge loss. But that's not what really made me throw up my hands and say "enough"...no, that was the speed. Even with just one computer backing up to it, the Time Capsule seemed terribly slow. Watching the progress indicator was just painful.
I put in a word about all of this to my independent Apple dealer, and they say I'm definitely not the first to complain about some or all of these problems. In fact, they told me they were going to set up a test lab in their shop to see if they could duplicate these findings. I have no doubt that they can.
There are a total of seven computers backing up to one Time Capsule. They all store maybe ~40GB worth of data including the OS. There are about six computers on the other. Because of the way the network is laid out, the Time Capsule is connected to a Gigabit switch (and that is the only thing it's connected to). It cannot be used as the router, although I know Apple suggests this. The Airport section is disabled--I have no need or desire to use it. Some computers link up at 100 megabits, others at 1 gigabit. There are no network problems--we have no problems moving large amounts of data across the same network to our tape backup machine.
Is anyone else seeing these kinds of problems? Am I doing something wrong or expecting too much from Time Capsule?

Answer 1

I may be on to something. The Time Capsules I have live in a telephone equipment room that is indoors but not directly air conditioned or heated. It doesn't ever get too hot to be comfortable in there--the highest I've ever seen the temperature was 80 degrees (F). Most of the time the temperature is between 60-78 degrees.
I happened to touch one of them the other day while it was in use, and I noticed that the casing was hot to the touch...not dangerously so I suppose, but much hotter than I would have expected.
So I turned a small fan on both Time Capsules and have left it running. And I've noticed that not only do backups seem to complete more quickly, the reliability is also better. I am going to try some of my most troublesome computers once again just to see what happens.
I know there is a fan pointed at the hard drive in the Time Capsule, but I can't see how it does much in the way of cooling things down. In my opinion, it's just surrounded by too many heat producing devices to do much good...after all, not only is there a 7200 RPM hard disk in there, but also a 500MHz Marvell processor and radio set.