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This post is not meant to scare anybody from dreaming about the AirPort Extreme and Time Machine from working well together, dream away, but that's all you'll get. My setup:

 

-MacBook Pro 2.0 CD (Not 802.11n)

-AirPort Extreme

-WD MyBook 320 GB

 

I was very excited to see how the AirPort Extreme would work with Time Machine and I found myself very disappointed. Just so you know, like all things Apple, setup was simple. Nothing could have been easier. I ran into problems when it took Time Machine at least 4 hours to complete a single backup. My MacBook Pro is only 40 GB full and I checked the "Skip system files" box. Bottom line, after some other testing of copying my iTunes library to the WD MyBook through the AirPort Extreme, it said it would take about 3 hours to copy my library. This could all be chalked up to me using 802.11g, but I do not have 802.11n and cannot take advantage of its speedier protocol.

 

Has anyone else attempted using the AirPort Extreme and Time Machine together?

 

Thanks.

Over 802.11n, it works great. I have seen backups at speeds near that of physically plugging the same hard drive into my MacBook Pro.

 

It is a little slower due to the overhead in the TCP/IP Protocol, however you should not be at that low of speeds.

 

For example, copying files between my MacBook Pro to my drive attached to my Airport Extreme, I can reliably move data at 2.5MB/s.

 

Yes, that was MB, not Mb.

Okay, over 802.11g (54Mb/s), I was able to push at 511KB/s (raw data speeds), 472KB/s (acutal throughout) for a 10 MB file and 493KB/s, 459KB/s on a 100 MB file.

 

So, significantly lower, and it looks like the TCP Overhead is sitting around 10% the actual reported speed.

 

So, the time you were seeing could be legit depending on the size of your backup.

 

Also note that your /Applications directory will still be backed up even if you select skip system files.

Hey again,

 

Thanks for your quick and detailed responses. So the good news is that it it's not me, the bad news is that it's the design of 802.11g. I guess its frustrating, but that's life.

 

Thanks again. And those of you reading this, the title of the post stands for 802.11g purposes, not 802.11n. If you plan on adopting Time Machine over your network, please be sure you have 802.11n machines running.

To say that it is the design of 802.11g isn't quite accurate. In truth it is a combination of factors.

 

1st of all, you require error checking on the wireless link because you have no assured delivery. That adds some overhead.

Next up, you are dealing with a packet based communication protocol instead of a flow-based one. That adds a little more overhead as you need to make sure that the data gets there.

If you are using encryption, you need to lower the TCP Window Size for the data itself to allow for obfuscation.

All of these "issues" still exist in 802.11n, however as you have higher throughput speeds, the overhead is not as severe as you see on 802.11g.

 

If you need wireless access to your hard drive for backup purposes, you really will need to either live with the reduced throughput speed of your current hardware or look at upgrading to a higher throughput speed via 802.11n.

 

Just so you know, you can upgrade the network card in your MacBook so that you can get 802.11n. Apple sells the card for $75, and most repair centers that I gave been to will install it for no charge.

Thanks for another well-informed post. Let me be clear, the intent of my original post was to warn those interested in using the AirPort Extreme as a router and USB server, be sure you know what you're getting into if you plan on using 802.11g. I have attempted just about all I can to boost my speeds, but it appears that it isn't my setup, its the nature of 802.11g. Yeah, G is fast for browsing and downloading, but it doesn't seem to cut it when transferring large amounts of data every single hour; for that you're going to want 802.11n.

That is very interesting. I'm going to check my settings and see if my setup has anything to do with it. Could you describe how you set everything up? Also, does Time Machine over the AirPort Extreme create a disk image of your data on your desktop as it transfers it to your HDD? Because it does with mine.

 

Thanks.

Yes, I'm replying to my own post. I wanted to update those following this because I have just reverted to my 10.4 install, reinstalled the AirPort Extreme and the thing is not necessarily "flying", but it is much faster than it was. I was able to copy a 1.25 GB file in roughtly 9 minutes. Now if I could only get those results with 10.5...

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