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MickeyZ · Apr 10, 2008, 07:53 PM

Hi all,
I have upgraded my MBP Core Duo (2.16GHz, 1st generation) to 802.11n using Mac Pro wireless upgrade kit card (Broadcom chip). The Airport card is recognized by the system as 802.11 a/b/g/n and I can connect to Time Capsule with link speed 270 Mbps if TC is setup to use 5GHz band with wide channels. However when I check the file transfer rate when copying files to TC's internal HDD the best I get is about 3.1MB/s. After installing the 802.11n card in the MBP I also reinstalled the Airport software from the TC's installation disk, but that did not improve the data transfer rate at all. I saw on the Internet that people are getting up to about 8-9MB/s data transfer rates after upgrading Core Duo MBP's with 802.11n cards, so there must be something I missed in the process. Any hints/help would be very appreciated.

Simon · Apr 11, 2008, 02:55 AM

TC disk read/writes are slow. You pay a penalty when TC bridges from 802.11 to SATA.

Those 8-9 MB/s over 5 GHz are real, but not to a TC disk. Try timing your transfer to another Mac. I get 7 MB/s over a mixed 2.4/5GHz 802.11n network easily.

/Applications/Utilities/Activity Monitor > Network shows a nice graph and the actual transfer rates. That should give you an idea of how much real world performance you're getting on that 270 Mbps network. But copying to the TC disk will benchmark the TC bridge, not the wireless network.

MickeyZ · 06:09 AM

Thanks for the info Simon. If what you're saying is true then it's quite disappointing, because wireless backup to TC was the main reason for upgrading my network to N. I would have thought that SATA interface is fast enough and together with N network speeds it should be faster than transfering files to an external HDD connected to regular G router. So it seems that the "TC bridge" Apple designed is very unefficient.

I also found this article: Speed test: Airport Extreme lives up to its name
He tested Airport Extreme, not TC, but with external disk connected to AE he got between 5.8MB/s and 6.8MB/s transfer rates on N network, which is much better than what I'm getting with internal SATA disk.

ghporter · Apr 11, 2008, 08:42 AM

Incremental wireless backups won't be a major problem with Time Capsule, as long as you do them regularly and fairly often. That keeps them smaller, which helps the transfer speed issue be less noticeable. ALL initial backups should be done directly connected with a cable to the TC-those are going to be monsters anyway, and it's just masochism to try to do an initial backup via wireless.

Just about the only thing I don't like about my CD MBP is that it doesn't have N wireless. I'll have to look into this hardware you've installed...

Simon · Apr 11, 2008, 09:46 AM

Originally Posted by MickeyZ

Thanks for the info Simon. If what you're saying is true then it's quite disappointing, because wireless backup to TC was the main reason for upgrading my network to N. I would have thought that SATA interface is fast enough and together with N network speeds it should be faster than transfering files to an external HDD connected to regular G router. So it seems that the "TC bridge" Apple designed is very unefficient.

Glenn has made an important point. While the initial backup will take long, future backups with TM will be incremental so 3 MB/s should be just fine for that.

Also, you should stick to Apple's advice. Do the first (full) backup to TC over Ethernet cable. Once, that is done switch to backing up (for the incrementals) over the wireless network. You'll see it will work just fine.

MickeyZ · 04:26 PM

I have done the initial backup over the wired connection. The issue I'm trying to understand and improve if possible is the higher throughput using N network. Before Simon explained that the transfer rate is affected by the 'TC bridge' I though I was missing something, but it looks like I might not be able to get a higher rates. And from the article I mentioned above it seems that an external HDD connected to AE (or perhaps even to TC) achieves better transfer rates.

With regard to the amount of data during incremental backups, in my case sometimes it's not very small as I mostly use MBP not connected to mains. Time Machine won't backup in such case, unless you explicitely force it to do so. It is supposed to be a 'background' process happening behind the scenes without requiring user interaction. So I either would have to manually start backups, or keep connecting MBP to mains.

I will test transfer rates from MBP to another machine connected to TC with ethernet cable to check if I can get 8-9MB/s.

Update:
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I run a few file transfer tests between MBP connected to TC over N network (5GHz, wide channels) and an old PC connected to TC over 10/100 Ethernet. I was getting up to 8MB/s, which is inline with what Simon said and what I read on the Internet. I will try to find more information about this 'TC bridge' slowdown issue. I would think it's rather software than hardware issue, and if so hopefully Apple will fix that in the future TC firmware updates.

MickeyZ · Apr 15, 2008, 06:32 PM

I've found this article on AppleInsider: AppleInsider | Exploring Time Capsule: 10/100/1000 Ethernet vs. 802.11g/n Wireless Networking
They got a transfer rate of 7.6MB/s while transferring gigabyte folder of data from MBP to TC over N network with 5GHz wide channels. So it must be possible to get better transfer. The question is how to configure TC/MBP.

Simon · Apr 16, 2008, 03:19 AM

Play with settings: channels, encryption, etc. And remove noise sources like cordless phones, etc. Also make sure you've set up TC in a good spot. For example next to large consucting surfaces/objects is a bad idea.

MickeyZ · Apr 16, 2008, 05:43 AM

I didn't know it is possible to change channel when using 5GHz band - when I select this band the channel setting drop-down menu has only 'Automatic'. After rebooting TC the channel used by TC is 36. How can the channel be changed in 5GHz band?

I'll play with the encryption settings, I will try to completely turn it off to ensure there is no overhead imposed by it. Regarding the placement of TC, when I do the transfer tests I have my MBP right beside the TC (~1m) and the link speed displayed in Network Utility is 270, so that shouldn't be an issue I think.