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Exploring Time Capsule: 10/100/1000 Ethernet vs. 802.11g/n Wireless Networking

post #1 of 22
Thread Starter 
Time Capsule, like most of Apple's earlier AirPort base stations, can handle both wired and wireless networked devices, but is optimized for serving wireless clients. This segment, the fourth of six exploring Time Capsule in depth, highlights the differences between wired and wireless networking on Time Capsule and the AirPort Extreme.

Time Capsule and the AirPort Extreme are designed primarily to serve wireless clients, providing a convenient and minimally invasive way to network systems in a home or small office to support centralized backups, file sharing, and media streaming. Wired Ethernet networking is nearly always going to be much faster, but also requires running wires through walls and tethering mobile devices to an Ethernet jack.

For the purposes Time Capsule is designed, including Time Machine backups and simple file and print sharing, the speed advantages of Ethernet are less of a factor compared to the needs of users who want a blazing, hard wired RAID array supplying high speed Network Attached Storage.

All of Apple's recent AirPort base stations have included an Ethernet switch, which allows user to directly plug in devices using an Ethernet cable; the base station bridges those wired clients to any devices attached wirelessly, so all can appear on the same AirPort created network.

However, while the AirPort base stations support full speed Ethernet switching, the shared disk file serving capacity of Time Capsule and AirPort Extreme is not tuned to saturate a big Ethernet pipe. That means the effective speed of the base stations' wired networking jacks are not competitive with a standalone NAS or dedicated file sharing computer. The numbers below (and chart on page 2) help outline that fact.

Real World Tests: Gigabit Ethernet vs 802.11n WiFi

Connected via Gigabit Ethernet to Time Capsule from a MacBook Pro, it took 1:38 to copy a gigabyte folder of mixed media to its internal drive. Including the few seconds it took for the sleeping Time Capsule drive to spin up, the operation took 1:45.

Wirelessly, it initially took a whopping 13:10 for the MacBook Pro to copy the same files to Time Capsule. In a parallel test, it took 8:18 to wirelessly copy the files to a drive connected via USB to an AirPort Extreme. The odd difference in speed was apparently related to the fact that in both tests, the MacBook Pro was wirelessly attached to the AirPort Extreme base station, which then wirelessly relayed the data to the Time Capsule, which was setup to "Extend a Wireless Network."

In that configuration, the MacBook Pro was skating across the wireless network twice to reach Time Capsule. With Time Capsule configured as the primary base station, the MacBook Pro took just 2:55 to copy the same files, a huge difference. Repeating the test again, it took 4:36 to perform the same action.

Repeating the gigabyte file copy test using a 5 GHz configuration took 8:17 and then 9:38 on the second try, suggesting that the 5 GHz setting itself isn't likely to make a huge improvement for typical users, and may instead just reduce their range and signal strength due to its worse signal penetration and radio power limitations. However, using wide channels, the same copy took just 2:11, indicating that in optimal conditions, 802.11n can easily compete with running wires in many applications.

The wild fluctuations in copy times over our wireless network links makes it harder to empirically compare wired to wireless times in a way that offers users with different configurations and different circumstances (such as the degree of outside interference, and the user's specific needs for wireless coverage area) a simple "rule of thumb" answer.

Below, we outline and present the results of various tests we performed to show you the range in performance you can expect to get wirelessly, compared to a wired network using Gigabit Ethernet, using Fast Ethernet (such as on previous 2007 models of the AirPort Extreme) and using 802.11g (on WiFi clients that do not support the full speed of 802.11n).

WiFi N vs Gigabit Ethernet and Multiple Users

In ideal conditions, 802.11n can perform at around three quarters the speed of Time Capsule's Gigabit Ethernet for a single user. However, if there are multiple users, each will eat into the limited, shared wireless bandwidth available. In a small office network, this favors setting up non-mobile machines to use Gigabit Ethernet rather than share the wireless network with mobile machines such as laptops. An Ethernet switch will allow each wired user to enjoy a fast, independent connection to the Time Capsule or shared AirPort Extreme drive, although at some point, concurrently connected users will eventually hit the limits of the drive and the data serving hardware itself.

For home users, an individual doing more than one thing, such as streaming AirTunes while running Time Machine, may similarly see a blip in their music playback performance every time Time Machine kicks in. Time Machine seems to momentarily overwhelm the wireless network when it first begins and again when it wraps up the backup session at the end, but counterintuitively, does not seem to excessively tax the network while it's actually backing up files in the middle of its session.

The design of Time Machine makes this issue easy to work around; if you're doing intensive network file operations or streaming media, simply turn Time Machine off to prevent any interruptions, and turn it back on again when its greedy use of the network no longer matters. Time Machine automatically accounts for lost time and catches up.

In our tests, configuring the network to use wide channels over the 5 GHz frequency made the network fast enough to accommodate both AirTunes and Time Machine at the same time without any hiccups. Attempting to dump the gigabyte of test files on the Time Capsule at the same time that both background operations where actively going on resulted in an estimate of 17 minutes from the Finder file copy, but didn't interrupt AirTunes playback. Time Machine took longer to perform its back up, but everything played along cooperatively, even as the reported signal strength fell down to around 216 Mbits/sec. The test files actually took 8:51 to copy during the AirTunes and Time Machine wireless smack down.

That indicates that for casual home and small office users, Time Capsule and the AirPort Extreme can support typical file sharing and Time Machine operations without any noticeable lag, if conditions are ideal, the configuration is optimized, and expectations are set realistically. For users with more demanding needs, a standalone NAS or dedicated file server connected to Time Capsule's Gigabit Ethernet switch might make more sense.

On page 2 of 2: Real World Tests: Gigabit Ethernet vs Fast Ethernet vs Wireless; and Real World Tests: WiFi 802.11n vs WiFi 802.11g.


Real World Tests: Gigabit Ethernet vs Fast Ethernet vs Wireless

If you have a Fast Ethernet version of the AirPort Extreme base station, you might be worried that you need to upgrade to Time Capsule in order to gain the faster speed advantage of Gigabit Ethernet. There is a small speed advantage, but it isn't the factor of ten that the theoretical throughput numbers suggest. Copying the gigabyte of test files via Fast Ethernet (10/100 Mbit/sec) to the AirPort Extreme disk from the same MacBook Pro took 2:45.

That's just 50% longer than using Gigabit Ethernet to access the Time Capsule, which may also enjoy a slight advantage in being directly connected to its internal drive over SATA rather than via USB; in other words, the difference in Fast Ethernet and Gigabit Ethernet isn't that dramatic. It also explains why Apple left Gigabit Ethernet off the original revision of the AirPort Extreme base station; Gigabit Ethernet sounds good, but the base station hardware can't take full advantage of the much bigger pipe.

Copying the same gigabyte of files to a PowerMac G5 acting as an AFP file server, the operation took 1:45 via Fast Ethernet. Using Gigabit Ethernet, the same files copied in 0:38. That indicates that the Time Capsule and AirPort Extreme are not the most ideal file servers for high performance users who have little need for wireless connectivity.

If you have an extra machine sitting around, it would no doubt make a much faster wired file server, although both of the base stations are much more compact and energy efficient than a PC or Mac set up primarily to perform file sharing; the base stations are designed primarily to serve wireless clients. And of course, Time Machine currently does not support backing up to other file server shares outside of the AirPort Extreme and Time Capsule, although this should be remedied soon in updates to Mac OS X Leopard.

Repeating the same file copy test to Time Capsule over Gigabit Ethernet, it took 1:37, almost three times longer than coping the files to the PowerMac G5 over Gigabit Ethernet. Wirelessly, copying files to the PowerMac G5 file server took 2:51; wirelessly copying directly to Time Capsule using the same network setup took 2:49. That means the standalone server was slower over wireless than Time Capsule, but considerably faster when using Gigabit Ethernet. Incidentally, in each of these tests, Time Capsule served as the wireless and Ethernet router between the MacBook Pro and the PowerMac G5 (which did not have its own wireless card).

While a standalone server can easily offer a significant edge in performance as a Gigabit Ethernet (or even a Fast Ethernet) file server, Time Capsule and AirPort Extreme are both equally as fast compared to a dedicated standalone server when serving the purpose they were designed for: wireless backups and effortless file sharing in a simple and efficient compact form factor. For users with needs for the performance of a wired network, there are more appropriate server solutions to choose from, from designating a machine as a file sharing host or setting up a dedicated server.

The chart below shows copy times in minutes:seconds, seconds, and megabytes per second, and graphs the performance on the right. We performed many of the tests twice to show the variance we saw in wireless performance even in back to back tests with no obvious variables changing. The results indicate that when used as a wireless device, Time Capsule is nearly as fast as when accessed by a wired client.

Again, note that these time reflect the performance of Time Capsule with little background competition from other clients. As multiple devices or background activities consume its wireless bandwidth, the performance of wireless networking will rapidly fall in comparison to wired clients, so while stringing cables can be unnecessary in an AirPort home, a small office using Time Capsule might want to diversify their network with an Ethernet backbone to support non-mobile clients.



Real World Tests: WiFi 802.11n vs WiFi 802.11g

Unlike the wireless networking tests, copying files over Ethernet resulted in far more consistent test results; there was no significant divergence between test times as there was when testing wireless connections. The variable results related to wireless networking times also suggests why reviewers reported a wide difference in the usefulness of wireless disk sharing on the MacBook Air.

With a poorly configured network, even 802.11n can be unusable slow, and in our tests, even older 802.11g devices could beat it in copy times. Set to optimize data throughput, base stations using a wide 40 MHz channel of the 5 GHz band should greatly improve the experience of users tied to WiFi, particularly Air users.

What about older clients that can't wring the wide channel performance from 5 GHz 802.11n networks? Using a PowerBook G4 with 802.11g, it took 7:21 minutes to copy the test files to Time Capsule, and that was through a secondary 802.11g router connected to the Time Capsule via Fast Ethernet.

That's no match for the 2 to 3 minute average of 802.11n in ideal settings using wide channels, but is actually better than the default configuration times experienced with 802.11n out of the box in b/g compatibility mode. The sweet spot of wireless networking is clearly targeted on 802.11n, but earlier devices can make reasonable use of Time Capsule and Airport Extreme shared drives.

The main advantage of upgrading to 802.11n for users with mixed wireless equipment is signal range; 802.11n devices use MIMO antenna technology to dramatically expand the coverage area of a base station. Even in situations where 802.11n isn't demonstrably faster than 802.11g, its wider range of coverage means the signal will not only be accessible to a greater area, but its speed will also hold up better on the peripheral edges of service.

Once you upgrade enough of your wireless devices to move to 802.11n exclusively (or create a hybrid base station network as described earlier with dedicated 802.11n service), you can take advantage of the other 802.11n trick: wide channels in the 5 GHz band that supply a major boost in network speed. Don't tell your neighbors or they'll flock into the 5 GHz band behind you and turn it into the same overpopulated wasteland that currently plagues many 2.5 GHz WiFi users in urban areas. Also note that in mixed mode, 802.11n networks momentarily slow down to g or even b speeds when older devices are actively transmitting data on the network.

The next segment will look at how the wired and wireless networking of Time Capsule and AirPort Extreme compares against performing Time Machine backups to a directly connected USB drive.

Previous articles related to Time Capsule and its AirPort Extreme cousin:

Exploring Time Capsule: WiFi 802.11n and the 5GHz band
Exploring Time Capsule: theoretical speed vs practical throughput
Exploring Time Capsule: how it fits into Apple's AirPort family
An in-depth review of Apple's 802.11n AirPort Extreme Base Station
Apple Time Capsule unboxing and preview
A Look Inside Apple's New Time Capsule
Answers to Time Capsule reader questions
post #2 of 22
Q: Does the Time Capsule's internal hard drive "sleep"?

It reads like you said it does. I've not heard about this before.
post #3 of 22
Quote:
Originally Posted by fuyutsuki View Post

Q: Does the Time Capsule's internal hard drive "sleep"?

It reads like you said it does. I've not heard about this before.

I'd imagine like any hard drive it'll naturally spin down when inactive.
post #4 of 22
Not all drives spin down when inactive. That's defined in the SMART parameters (smartctl or hdparm), and the controller.

Sheldon
post #5 of 22
Quote:
Originally Posted by abrooks View Post

I'd imagine like any hard drive it'll naturally spin down when inactive.

It does. And quite annoyingly it does it quite fast. After about five Minutes it goes to sleep.
And much to my despair there is no setting to control the time it waits before it goes to sleep.
That might not be a problem if you want to use Time Capsule as a backup unit only, but if you want to access the TC continuously (because you configured it as a network drive and have for example your iTunes library stored on it), it starts to annoy a bit. Imagine you are listening to an album in iTunes, all tracks with a duration of more than five minutes (not uncommon with live concerts, etc). After each track iTunes will come to a halt while waiting for the next track since the TC went to sleep in the meantime and the wake-up-process of the disc takes about 6 to 10 seconds every time. Such a delay-setting would have been a nice thing to have.
post #6 of 22
This brings me to the question if anyone knows if an external USB Hard Disk connected to the Airport Extreme ever spinns down?

I am thinking of an external 3,5' WD Book Series...
post #7 of 22
Quote:
Originally Posted by BandiTT View Post

This brings me to the question if anyone knows if an external USB Hard Disk connected to the Airport Extreme ever spinns down?

I am thinking of an external 3,5' WD Book Series...

I'd like to know that as well. Right now I'm planning on hooking up an external drive to my old PPC mini (Fast Ethernet) and using that for Time Machine backups. The mini was clearly faster than the Extreme's USB port, and it will put a FW drive to sleep when it's not using it. That's not generally the case with USB drives. That being said, if you are planning on one of WD's My Books. From what I've heard, those drives will put themselves to sleep after a certain period of inactivity. They don't wait for the computer to spin them down. According to WD's web site, they are designed specifically to do just that. So it may be a non-issue for you if that's the drive you get.

Also, from the article: "Time Machine currently does not support backing up to other file server shares outside of the AirPort Extreme and Time Capsule, although this should be remedied soon in updates to Mac OS X Leopard."

I don't believe that is true. Apple has always said that you can use Time Machine to backup to a file share that is being hosted by a Mac running Leopard. That's why I was planning on using a drive connected to my mini to back up my MBP.
post #8 of 22
Quote:
Originally Posted by BandiTT View Post

This brings me to the question if anyone knows if an external USB Hard Disk connected to the Airport Extreme ever spinns down?

I am thinking of an external 3,5' WD Book Series...

I have a WD MyBook Pro hooked up to my Airport Extreme. It does spin down when inactive for a certain period of time. The light on the drive, however, stays on. This was the response from WD when I asked about the light being on:


It is normal for the drive to remain on when connect to the Airport, although, the drive in the enclosure will spin-down after ten minutes of inactivity.

Sincerely,
John E.
Western Digital Service and Support
post #9 of 22
Quote:
Originally Posted by pup975 View Post

I have a WD MyBook Pro hooked up to my Airport Extreme. It does spin down when inactive for a certain period of time. The light on the drive, however, stays on. This was the response from WD when I asked about the light being on:


It is normal for the drive to remain on when connect to the Airport, although, the drive in the enclosure will spin-down after ten minutes of inactivity.

Sincerely,
John E.
Western Digital Service and Support

Thank you for this information. I was not sure if the Extreme will keep the USB Disc alive, as I had seen with an older drive of mine. The WD MyBook might just be what I need then
post #10 of 22
Nice info guys.


Whimsical:

I host my iTunes collection on a tasty 1 TB Newertech MiniStack (with Western Digital Green Power hard drive) which I bought both for ports and its sleep mode. I fitted the drive myself. I have my Mac mini set to sleep its drives with 3 minutes of inactivity (I like to keep it quiet), but iTunes seems to be smart enough not to interrupt music even with such a short stop. It only lets the drive power down through lengthy podcasts, not even during my 10 minute + Velvet Underground live sets

It's connected by FireWire right into my Mac mini, which runs iTunes. Perhaps it works better when you're using a local disk instead of a network volume.

As for how to alter drive power down times, there's a command called pmset you can use at the command line. But that will only work for local drives (ie. do it on the host machine) and won't override the modern sleep behaviour others have posted about.
post #11 of 22
Quote:
Originally Posted by AppleInsider View Post

With a poorly configured network, even 802.11n can be unusable slow, and in our tests, even older 802.11g devices could beat it in copy times.

That one kinda jumped out at me... you might want to fix it.
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17" i7 Macbook Pro (Mid 2010), Mac Mini (early 2006), G3 B&W, G3 Beige Tower, 3 G3 iMacs (original, bondi, snow), Power Mac 7600/132, Power Mac 7100/100, Power Mac 6100/60, Performa 5280, Performa...
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post #12 of 22
The minute:second and seconds comparisons in the chart are inconsistent. For instance, the first row reports a minute:second time of 1:38 which is 98 seconds. It appears the conversion was based on a factor of 50sec/minute.
post #13 of 22
You folks know very little about Network Design and Performance optimization and that 13 plus minute should have been a big clue right off the bat.
post #14 of 22
Has anyone tested Apple's Time Capsule with a Western Digital My Book World Edition II external hard drive? It uses a 1000 Ethernet connection. I'm wondering how fast a 1 GB file transfers over WLAN 802.11n when an external hard drive is connected via Ethernet cable and not USB?
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post #15 of 22
Quote:
And of course, Time Machine currently does not support backing up to other file server shares outside of the AirPort Extreme and Time Capsule

Not true - you can TM to any AFP server on your network... I was using a PowerBook G4 as m TM backup target for all of our Macs until I got my TM.
post #16 of 22
Hi,

is there any way to prevent the TC spin down?

I really hate this "feature"..

Thanks in advance!

Kind Regards,
nszb
post #17 of 22
You can probably craft a script to touch a tiny file off TC every 4 minutes or something.

Try automator to see if you can't just read an empty directory on the TC and use Automator workflow looping to repeat. Something like check a directory, delay 4 mins and then rerun.
post #18 of 22
post #19 of 22

Thanks a lot!
post #20 of 22
One thing that is not very clear to me:
I would like to add a My Book raid solution on the time capsule's USB port. Now I learned the drive will go to sleep without the ability to change the settings.
My photo, music etc will be placed on this drive, such that i can (wirelessly) access them on my macbook.
A long story short: if the My Book goes to sleep, will Time Capsule (or macbook for that matter) wake this disk up such that it can be approached ? This may sound dumb, but I would like to prevent ending up plugging and unplugging cables, push buttons or so, every x minutes.

many thanks!
MacBook 13.3" (intel)
Time Capsule 500 GB
Airport Express
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MacBook 13.3" (intel)
Time Capsule 500 GB
Airport Express
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post #21 of 22
I've a "MyBook" 1TB drive plugged into a Time Capsule... the drive does spin down to some sort of "sleep" when it's idle, but as soon as one of the computers tries to access it, it spins up... just takes a few seconds to get any data from it at that point.
What I will add, If you shut your computers down, set them to automatically mount that HDD at startup, the computer needs to see a mounted drive to perform automatic functions, like backup/time machine.
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From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, "Look at that!" -...
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post #22 of 22
OK, I got it all to work. USB drive connected to the TC: great so far. Now next is that I want to backup the drive connected to the USB port of the TC to the TC itself. Preferably with TM. I haven't found a way to do so. Does anyone have an idea? Or should I use tools like e.g. Synk to do this? Less neat of course, since TM would be my preferred solution.
MacBook 13.3" (intel)
Time Capsule 500 GB
Airport Express
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MacBook 13.3" (intel)
Time Capsule 500 GB
Airport Express
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