Apple boasts that their AirPort Extreme base station is "5x faster" but which devices can connect?

Apple is not always quick to support new technologies, but they threw their weight behind 802.11n Wi-Fi as soon as hardware was available. They upgraded their access points, laptop and desktop computers beginning in 2006, though support importable devices lagged. But the capabilities of 802.11n devices varies widely, and today’s Apple devices are no exception.

802.11n Capability Refresh

Routers like this Cisco E4200 can hit 450 Mb/s data rate!

As I discussed in detail last week, there are four main technology enhancements to 802.11n: MIMO and multi-streaming, 40 MHz channels, 5 GHz radio spectrum, and various packet enhancements. Each of these is optional for 802.11n devices, and Apple has picked a subset to support.

Basic 802.11n devices operate in the same 2.4 GHz radio channels as earlier Wi-Fi technologies. Many also lack the multiple radios and amplifiers required for multi-stream performance, and Apple only supports 40 MHz channels in the 5 GHz range. This means that simple devices are limited to a data rate of 72.2 Mb per second. These compromises are often made to conserve power or due to physical space constraints, so portable devices like the iPhone lack the performance of full-fledged computers.

Most desktop and laptop implementations of 802.11n include radios capable of either 2.4 GHz or 5 GHz operation, and many offer two or three antennas for MIMO and multi-streaming. From 2006, Apple has offered 802.11 draft-n wireless cards in their laptop and desktop line, and all of these boast dual stream, dual frequency radios. Beginning in 2011, Apple has introduced ultra high-performance Wi-Fi offering three spatial streams and up to 450 Mb per second data rate.

When it comes to access points, Apple has aggressively moved toward 802.11n but lacks many of the features found on competitive products. The Apple AirPort line of Wi-Fi access points currently includes both the AirPort Express, with selectable frequency and dual stream support, as well as the AirPort Extreme, which supports both frequencies concurrently as well as triple stream performance. But Apple does not allow multi-streaming or 40 MHz channels in the 2.4 GHz frequency range on any device in their AirPort line.

Apple 802.11n Wi-Fi Device Capabilities

You might also want to read Which iPad is the Best Choice? and Decision Point: Comparing the 2011 MacBook Pro Models

To try to alleviate the confusion around which devices support what 802.11n features, I created the following table. Generally speaking, any Apple access point, laptop or desktop built since 2006 includes selectable 2.4 or 5 GHz support and at least dual stream capabilities. Every Apple TV also includes 802.11n Wi-Fi right out of the box. On the portable device side, both iPad generations, the iPhone 4, and the latest iPod Touch support 802.11n, though performance is limited.

Apple Devices with Limited 802.11n Support

I love my AirPort Express, but it's limited to two streams and either 2.4 or 5 GHz

Apple’s portable devices sacrifice performance for efficiency when it comes to Wi-Fi. The iPhone 4, 3rd generation iPod Touch, iPad, and Apple TV each have just one Wi-Fi antenna, so they are limited to single stream performance. The iPhone 4, iPod Touch, and first-generation iPad also lack 5 GHz radio compatibility, though the second-generation iPad and Apple TV do include it. This means that households with these popular devices cannot use 5 GHz-only networks, making the dual-band AirPort Extreme more attractive as a base station than the switchable AirPort Express.

Unsupported Apple Devices

Many readers will find that they own devices that do not support 802.11n at all, forcing them to maintain backward compatibility when deploying new Wi-Fi routers. Some very recent devices, including the iPhone 3G S and previous and the first three generations of iPod Touch, require 802.11g to connect. On the computer side of things, pre-2006 MacBook, MacBook Pro, and iMac computers lack 802.11n compatibility. But the Mac Mini is the real standout: It didn’t include 802.11n until the Core 2 Duo refresh in early 2009.

Stephen’s Stance

Apple's 5th-generation AirPort Extreme can hit 450 Mb/s data rate in combination with the 2011 MacBook Pro and iMac

It is nice to see Apple out in front with a technology like 802.11n, considering their reluctance to support Blu-Ray and USB 3.0. Although expensive, the AirPort Extreme and 2011 MacBook Pro and iMac sport top-of-the-line specs and high performance Wi-Fi. But the lack of 5 GHz support across the board means many users will stick to the crowded 2.4 GHz spectrum, limiting performance. And I’m sure owners of recent but unsupported devices (the older iPhone, iPod Touch, and Mac Mini) will be disappointed to have to stick to 802.11g.

© sfoskett for Stephen Foskett, Pack Rat, 2011. | Which Apple Devices Support 802.11n Wi-Fi?
This post was categorized as Apple, Everything, Personal, Terabyte home. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

Have you seen this dialog box? Is it an error or a help?

But Apple recently rolled out a ”Time Capsule Backup Update”, and included it in Mac OS X 10.6.4, that is causing confusion and concern. In the name of improving “the reliability of your Time Capsule backup,” this update has the unfortunate side-effect of detecting errors in existing backup bundles and forcing users to start a new backup. It happened with two of my Macs so far, so I was keen to find out what’s going on.

Verifiably Bad

Time Machine may look simple, but it’s an incredibly complex piece of software. It uses multiple kernel-level features and builds a complete files-level copy of your data in a “bundle” that acts like a virtual drive. Rather than storing files multiple times (which would be space-inefficient) or hard-linking them (which is efficient for space but would take a long time), OS X adds directory-level hard links, a fairly new concept. So if no changes have been made in your /Applications directory, it just creates a single link to a previous copy. OS X also includes a new daemon to monitor changes on a directory basis, which is also fairly cool in a geeky sort of way.

This intricate but powerful system can lead to trouble, however. If a backup process is interrupted while it is working, the relationships between directories, files, and dates can become corrupted. This is especially common for network-mounted drives, explaining Apple’s reluctance to allow non-Apple NAS units to be backup targets. But even local direct-attached drives can sometimes become corrupted over months of operation.

As (poorly) explained in Apple’s Knowledge Base article HT4076, corruption can cause previous Time Machine backups to be unavailable. So Apple introduced a more-robust mechanism to check backup integrity and rolled it out in Software Update and as part of OS X 10.6.4. It scans old backups and, if errors are found, flags them read-only and starts a new backup bundle. See this Apple Support Discussion thread and this web site for more information.

What You Should Do

Let’s cut through the confusion caused by Apple’s typical lack of explanation.

Should you install this update? Yes! Corrupt backup images are bad, regardless of the cause, and you need to know whether yours is good or not. Installing the update might cause you to start a new backup bundle, but at least you’ll know your data is safe!

Should you click “Start New Backup”? Not yet! If you see the dialog above, your existing Time Machine backup is corrupt, and you might not be able to recover data from it. But you can save a copy of the corrupt bundle and, perhaps, extract some data from it if needed.

Ask yourself if Time Machine has saved data you might need before deciding what to do next:

1. If you are sure you won’t need anything backed up before today, click “Start New Backup” and let Time Machine do its thing.
2. Otherwise, click “Back Up Later” and save a copy before letting Time Machine start a new backup. Just look for a file called “computername.sparsebundle” (for network backups) or “Backups.backupdb” (for local ones) and create a copy with a different name. You can open sparsebundle files with DiskImageMounter and browse them like any other disk. More information is available here.

There you go. If you click “Start New Backup” when you see this dialog box, Time Machine will erase all of your old backup data and start a new bundle. It won’t be corrupt, but it will be empty.

Note that you can manually initiate a Time Machine backup integrity check by option-clicking the “Time Machine” icon in the menu bar and selecting “Verify Backups.”

Stephen’s Stance

Backups are good.

Corrupt backups are bad.

Time Machine encourages backups, and works pretty efficiently, so it’s good.

This update ensures that Time Machine’s backups aren’t corrupt, so it’s good.

‘Nuff said.

© sfoskett for Stephen Foskett, Pack Rat, 2010. | “Time Machine completed a verification of your backups. To improve reliability, Time Machine must create a new backup for you.”
This post was categorized as Apple. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

Homes now need data storage as well as closets...

This is part of an ongoing series of longer articles I will be posting every Sunday as part of an experiment in offering more in-depth content.

Along with my professional focus on enterprise storage systems, I’m enamored of home networking, and recently passed the three terabyte mark at home! This got me thinking about where home storage is heading.

As you can see in the photo, my office closet is overflowing with computer equipment (and one sweet guitar), but my data storage is much better organized. I have a hacked Linksys NSLU2 with 500 GB as a file server, a 500 GB PC backup disk, a 160 GB Time Machine disk, 1 TB of TiVo storage, and the rest. But wouldn’t it be nice if this could all be combined into some kind of super home server?

Past Failures: Home Servers

Home storage appliances and servers have come and gone over the year, with none seeming to make much of a mark. The market remains littered with UPNP media servers and home NAS boxes dashed on the shoals of an unappreciative public. Nearly every home network device company has produced one or two home storage servers, none of which have succeeded. Although I use a Linksys NSLU2 at home, I had to hack its Linux software and completely replace Linksys’ features to create a useful device! The un-hacked NAS devices of Buffalo, Western Digital, Netgear, and the rest have generally failed to find buyers as well. So far, consumers seem content with simple USB and FireWire external drives.

The most adventurous home storage servers came from Zetera and Ximeta, both of whom relied on proprietary IP SAN protocols. Note that these were SAN products, sharing block storage over Ethernet, rather than conventional NAS solutions. Both required drivers, limiting client support. The one Zetera buyer I know was pleased by the performance but never used the device as anything but a large hard drive for one PC.

Then there is Microsoft. Recall that the latest Windows Home Server is only their latest attempt to enter this market, and yet I know of no one who has adopted the device. The same can be said of the various media center servers from Microsoft and others. At this point, it seems likely that the future of home storage servers will not come from Microsoft, though their two XBox generations have great potential as clients.

Even EMC has entered the market with their nifty (but largely unnoticed) LifeLine product and Iomega acquisition. Supporting file services and backup for computers as well as audio and video for media players, EMC positions LifeLine much like their Retrospect backup product, but goes further in offering a complete software solution for hardware OEMs wanting to offer a non-Windows home server. Although an impressive offering, it is too early to tell if EMC will have much success with this product.

The Sleek, Shiny Elephant in the Living Room

Of course, there is one company that sells media players and servers by the bushel, complete with sleek, shiny interfaces. Apple’s tremendous success with the iPod has led to their iTunes software becoming the dominant media organization platform, complete with its own proprietary discovery and sharing protocol. Now, with the Apple TV and video iPods, the company is broadening into more media categories. Surely their dominance here puts them in a special position when it comes to setting the stage for a home server or storage revolution.

They also have a strong position in the world of dedicated home storage. Their Airport products are among the only routers to be widely implemented with shared storage. Although many other companies offer similar products, low customer understanding means that these functions are not widely used. And the new Time Capsule device is surely already the most widely-used home NAS product.

But Apple has not yet shown any home server strategy. Administering multiple iTunes servers can be frustrating for users, with no inter-iTunes synchronization or centralization capability. Although the Mac Mini, Apple TV, or Time Capsule could certainly be seen as a home server, the company does not position them as such in the market. Indeed, some iTunes users like myself rely on compatible third party media servers like Firefly and TwonkyVision rather than using iTunes itself. Still, rumors of an Apple home server persist.

One issue for Apple is their reliance on proprietary protocols. Although the Bonjour discovery protocol is certainly simpler than UPnP in practice, Apple stands alone in relying on it. They also steadfastly stick to AFP for NAS and DAAP for remote media streaming. This limits the number of third-party clients and servers that can be used with their hardware and software.

The Future is Friendly

Although Apple has not yet tipped a home storage strategy beyond Time Capsule and Airport Extreme, they are best positioned to deliver a real home storage solution. A simple step would be to create an iTunes media server integrated with Time Capsule and add client/server media synchronization. The company already has OS X backup and file services integrated, and this move would further centralize the digital home around Apple products. But the company’s reliance on closed protocols like DAAP is worrisome, since it locks consumers into nearly all-Apple solutions.

Microsoft’s Media Center and Home Server combination, based around UPnP, shows great promise, with many compatible third-party clients and servers already available. But my own experience with the solution has not been at all positive (I still can’t get my Roku SoundBridge, Vista Ultimate laptop, and Media Center PC to see each other!), leading me to question the viability of this option.

Although Apple or Microsoft could come to dominate, I suspect the future of home storage is out of both companies hands. A number of others are working on improved home server experiences, including EMC’s LifeLine and the expanding use of Debian Linux and open source tools. But all could be sidelined by improved Internet-based services. Google, Microsoft, and Apple continue to expand their online consumer suites with greater storage, synchronization, multimedia integration, and all have the potential to reduce or eliminate the need for in-home storage.

Although I cannot yet tell which service will win, one thing is certain: Consumers demand friendly, flexible solutions. They don’t want to fuss with their media, and they don’t want simple shared storage. They want integration with multiple devices and flexibility to access their content on any device. The first company to offer a simple, flexible storage server for the home will surely be on the right track!

© sfoskett for Stephen Foskett, Pack Rat, 2008. | The Future of Home Storage
This post was categorized as Apple, Computer History, Terabyte home. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.