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Thursday, March 06, 2008, 08:00 am PT (11:00 am ET)

Answers to Time Capsule reader questions


Disk Performance over the Network

Frank R. asks: "If my network goes down (or I just don't feel like using it) can I just plug my computer directly into Time Capsule to access my stored data?  if so, what is the improvement in transfer rate?"

Yes. The improvement is substantial, as noted below.

John Contarino asks: I am wondering if I can backup to Time Capsule through Ethernet? I could then use Time Capsule as my external hard drive for Time Machine as well as my wireless base station. Or would it be better / faster for me just to get an external Firewire drive and use that for Time Machine.

Yes. Over Gigabit Ethernet, backups and file access are dramatically faster than wireless, but not as fast as a directly connected Firewire drive.

Martijn B. from the Netherlands asks: "Provide specific attention to the Time Machine user interface when browsing through files and through time, which I find very jerky when using the USB hard disk connected to my Airport Extreme (after 'hacking' the system preferences). Big improvement however since the previous bug fix in Leopard, before which it didn't work at all."

Paul A. of Compuware volunteered an answer: "I suspect you will receive a flood of requests for comparisons of performance in accessing the Time Capsule internal hard drive versus the AirPort Extreme with an external USB 2.0 drive. In my experience with the AirDisk (i.e., AirPort Extreme and external Western Digital "Mybook" drive), I concluded that a significant limiting factor was network speed.

When first deployed, I had yet to upgrade my network architecture to Gigabit Ethernet. At that time, I noted the following behavior:

Copying large files to the AirDisk, I found performance not blazingly fast but acceptable.
Copying thousands of small files to the AirDisk, as would be typical during a backup, was painfully slow.
The shared 180GB iTunes library on the AirDisk was sluggish but usable.
The shared 10GB iPhoto library on the AirDisk was slow to the point of being unusable.

After a month, I upgraded my network architecture to fully support Gigabit Ethernet. I immediately noticed a huge increase in performance when accessing the AirDisk. Copying thousands of small files was still noticeably slower than copying larger files but quite acceptable. Using the shared iTunes library was only slightly slower than with a locally stored library. The shared iPhoto library was not as snappy as a local library but infinitely more usable than before.

While a bit long-winded, my overall point is that a proper test of the hard drive performance should attempt to remove the network architecture as a limiting factor. If the AirPort Extreme / TimeCapsule and connected computers are all using Gigabit Ethernet, you'll get a much better comparison of hard drive performance. You do this for a living, so you probably planned for this contingency already. ;-)

A second point is that a large iPhoto library is a good barometer of the comparative usability data on the network drives. If you have a hefty iPhoto library available, you might try this. The Event view in iPhoto is especially demanding as you scroll through thumbnails.

That provides a pretty good outline of what users can expect in terms of WiFi to share files and media libraries. We are still working on measuring benchmarks between wireless use, Gigabit Ethernet, and directly attached USB or Firewire drives.

Time Capsule Disk Formatting

Franco V. from Italy asks: "Option to reformat the internal disk with HFSX Case Sensitive?"

No, the AirPort Utility software has no provision for changing the disk format. However, the drive is being read and served up from the Time Capsule (or Extreme) itself, and presented as a shared volume. That means the unit's firmware would also need to be case sensitive savvy.

Joerg E. from Germany asks: "If you make Time Machine backups on a local USB drive, it creates a copy of the original files as a regular file system using hard links. On the other hand, if you make backups to a hard drive on another Mac in the local network, it creates a sparse image file, very similar to FileVault in Leopard. Myself, I feel much more comfortable with the regular file system, knowing I can always get direct access to the backed up files."

Yes, Time Machine always uses sparse image files to save backed up files to network volumes. This allows it to use hard links within the HFS+ disk image even when that image is saved on a foreign file system that does not support HFS+ features.

Joshua B. asks: "In your review of Time Capsule, would it be possible to remove the hard drive, replace it with a new one, and see what happens?"

The drive is erased and set up for use with the device, just as with plugging in a blank USB disk.

RAID and Disk Spanning

John N. of Minnesota asks: "Does is allow two (separate but identical) external hard drives that are configured to be RAID 1 to be attached and recognized? With the Extreme, the drives need to be in one enclosure acting as a single drive in order to be recognized."

Neither the Extreme nor Time Capsule does any RAID striping or mirroring on internal or attached drives. To use a RAID volume, it would need to be a self contained unit with a USB interface.

Tadd T. asks: "If I attach an external drive to a time capsule, will the Time Machine see the two drives as one backup device?  I ask this because my Mac Pro has 2GB of HD and I'd really like to find a backup target that is > 1GB so I can do a more complete backup.  Time Machine so far seems to not be able to span multiple volumes with its backup even if it is backing up multiple volumes from the client computer."

Neither the Extreme nor Time Capsule does any JBOD concatenation or disk spanning on internal or attached drives. To use a series of volumes acting as one large logical drive, it would need to be a self contained unit with a USB interface.

Disk Performance

Adam T. asks: "I was wondering if you could find some way of evaluating the actual hard drives.  This is apparently "server grade" but I have no idea what that means.  For example, am I better off getting a 1TB version, or connecting a 500GB drive to a 500GB model?  How would this stack up versus a G-Raid drive?  How about against a myBook drive, etc.?"

If you're planning to use Time Capsule or any other wireless server product, the speed of the drives and of the server will have no impact on throughput because the weakest link will be the wireless network. Any speed advantages would only be visible to computers attached directly to the wired LAN using Gigabit Ethernet. We are still doing performance testing to benchmark how great of a difference this makes, but it will be very similar to the performance of the AirPort Extreme.

Disk vs Printer Sharing

Theo K. asks: "I was wondering since the time capsule has only one USB connection which would requiring I guess a USB hub for additional connections. Can the review include testing of an attached USB printer to share and an external USB disk to backup to and see if they work alright at the same time, if printing is disabled while a backup is in process or does the backup pause while printing and then automatically resume where it left off."

We can test and update this later, but there should be no significant interruption of printing when using file sharing. Any use of the wireless network will be impacted by performing backup operations, but following the first full backup, Time Machine typically only has a small number of files to transfer in subsequent backup sessions.

Upgrading or Expanding an Existing Network

Bob B. in Ohio asks: "In your upcoming review of Time Capsule, it would be great if you could comment on the difficulty of using Time Capsule with an existing wireless router. I have a 2Wire DSL combination modem / wireless router, and I've read that it can be difficult adding another wireless router (Time Capsule) onto the LAN. Perhaps the trick is to disable the 2Wire wireless feature - I'm not sure. It almost appears, from the preliminary overview in Appleinsider, that Time Capsule handles this during the initial configuration. That would be awesome."
 
It is much easier with the new setup assistant to import the existing network setup from an existing base station to the new one, or to choose to add Time Capsule to an existing network to extend it rather than replace it. If you are using a DSL router, Time Capsule wouldn't replace the unit entirely but could either extend the existing network, providing faster 802.11n service, or replace the DSL router's wireless functions. There is still some complexity involved in setting this up. Extending the network would be the easiest option to follow.

Ted D. asks: "How do I setup the system so that I can replace an existing Airport base station, yet still use that station to extend the network to a different part of the house. That is, I want take my cable modem off the old Airport, put it on the Time Capsule, yet still be able to use the old Airport to extend the range of the network and be able to attach a network printer.

The easiest and ideal option is to extend your existing network with the Time Capsule, leaving any slow devices connected to your old base station and using the Time Capsule with 802.11n devices. An extended network shares the same DHCP server and address space, which prevents problems with seeing shared files and libraries on the local link network.

On page 3 of 3: Time Capsule with AirTunes, Xbox, Linux; Network Sharing; Power Consumption; Time Capsule as a Media Library Server; Mixed Wireless Network Performance; and Shared Disk Reliability Compared to AirPort Extreme.