Very soon, Apple's Time Capsule (ATC) will be available. It says on the paper that it's meant for using with Time Machine. Great, isn't it? The possibility of sharing a hard drive among a set of machines is great. The possibility to have backups as soon as one's wifi-connected is great too. The combination of them both is even greater. But...

Well, I don't have any ATC, but now I have an Airport Extreme Base Station (AEBS) (the Gigabit version). I plugged a very efficient USB hard drive (Western Digital, "Studio", 1TB), and played a few minutes with a MacBook Pro (Core2Duo, 2.16GHz) connected to it. So the very first point is that it's very easy, anyone who can use a Mac can configure the disk (at least I think and hope so...). The second point, which is (really) surprising (to me) is the transfer rate.

Connected via IEEE 802.11n (approx. 100Mbits/s) the transfer rate I saw was about just a *single* MB/s, which is *really* bad! So I went on searching why I had such a transfer rate. Then I read some people advise to disactivate journaling. Okay then, let's turn it off... Well, the transfer rate was then multiplied by 3 to 4 times! Well, so it's clearly the AEBS's embedded chip that's poor in performance.

Let's go back to ATC. First, a AEBS combined with a USB hard drive is definitely *not* equivalent to an ATC (even if one adds a USB HUB), and that's because (at least *today*), one cannot make Time Machine use a AEBS shared disk, whereas it's ATC's (commercial -okay-, but also technical) purpose.
Well, that leads us to two questions:

1. Will Apple update the AEBS's firmware such that one can use the AEBS' shared disk as a usable disk for Time Machine?
2. Is one ready to accept the same poor performances on transfer rate on the ATC as with the AEBS?

I wouldn't pay for an ATC if the transfer rate is so poor! Nowadays machines have easily hundreds of gigabytes to backup, and if the very first time Time Machine puts all the to-backup-data to the remote disk is at like 3MB/s, well, it'd be just so pitiful I personally couldn't stand it. Still, even poor, it'd may be usable/acceptable (but not for me) if one started with an empty system (empty home directory).

So, what's your bet?

Notes about performances: a one TB hard drive can easily have a sequential sustain read/write rate of 70MB/s. USB2 limits to about 25MB/s at full speed generally, and if you're lucky it might come up to 45MB/s (mostly because there is *no* DMA (direct memory access) possibility with USB). No DMA means that every bit must go though the CPU before you can do anything with it. (Apple's) 802.11n (currently) limits to about 130Mbits/s (that's about 16MB/s) if you're lucky, and the Ethernet Gigabit connection limits to about 100MB/s (theoretically to 125MB/s). So with the AEBS it's clearly the embedded chipset that limitates the data transfer rate.