Time Capsule review

Time Capsule takes the functions of an AirPort Extreme base station and adds an internal disk that allows Time Machine to back up over a network.

Since it was announced in January, many have been eager to take advantage of wireless backups - a feature that once seemed destined for general use in Leopard but for now is reserved for Time Capsule owners.

At 3.2cm wider and longer, and just over 2mm higher, the Capsule's footprint is larger than that of the Extreme and the Mac mini, inevitable due to the internal disk. Typically there are no visible vents but Apple mentions that the case will dissipate heat, as borne out during our lengthy first backup. The warmth didn't feel excessive.

At the rear are four Gigabit Ethernet ports - one for connecting to the outside world via DSL or cable modem, and three to connect other devices. A single USB port allows a printer to be shared, while storage can also be added this way. Both can be attached using a hub as well.

Our first backup ran from an 802.11g-equipped PowerBook over the capsule's 802.11g wireless network. No other machine was connected, nor was the PowerBook doing anything else over the network. The devices were in close proximity to ensure a good signal; others that cause interference, such as cordless phones, were kept away.

Over five hours Time Machine backed up 10GB of a 60GB system drive. The remainder of the backup was performed over an Ethernet cable. Apple recommends doing so for initial backups and we wholeheartedly concur, especially if backing up a handful of Macs, which could otherwise take days to complete.

Unless you limit the Time Machine backup to include only your documents folder the initial backup will take some time regardless of the connection used. Subsequent backups are less noticeable and you'll quickly become used to the neartransparent process working in the background.

Rather than indicating poor performance of the capsule, the first backup is related to the number of files processed and overheads from Time Machine. Performance was markedly better when copying dummy disk images of 100MB, 500MB and 1GB directly to the Capsule.

Over wifi, these files took 40 seconds, 3 minutes 21 seconds, and 6 minutes 46 seconds respectively - a roughly linear relationship. Over Ethernet, performance was expectedly fast, taking 59 seconds for the 1GB file.

Backing up 100MB, using Time Machine, took much longer - over 2 minutes. This is because the software has to assess what has changed and maintain a temporal record of what has been backed up and when. Time Machine mounts its backup as a disk image - with Spotlight briefly indexing it, there's a nominal penalty here too.

Time Capsule provides more than backup functions. Its duplication of AirPort Extreme's capabilities allows it to add wifi to an existing cabled network or replace a slower wifi network to give more comfortable bandwidth.

The router features are comprehensive enough including WPA2 security, a Nat firewall and MAC address filtering and time-limited access based on MAC address. They are configured through AirPort Utility 5.3, supplied on CD and required for Time Capsule. A minor update with unspecified fixes was released shortly after shipping.

The utility also allows the disk to be erased with the same quick or multi-pass options as Disk Utility provides for locally attached storage.

Strangely, integrity checks on the internal disk aren't available, which fills us with some unease about using it for anything more comprehensive than Time Machine backups. There's also no provision for how much storage will be used for Time Machine backups, so anyone working in a multi-user environment needs to take care that they aren't filling the drive and preventing other Macs from backing up.