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Mac OS X 10.7.4 Finally Fixes WebDAV (and iDisk)

Friends, Mac users, naysayers, I come not to bury iDisk, but to praise it.

Praise iDisk? Really? Now?

If you have updated to Mac OS X 10.7.4, give iDisk another try. It is leaps and bounds faster than before. One might even call it usable. And it will remain so until… MobileMe’s sunset on 30 June 2012.

What? Apple finally fixed iDisk now? On the eve of its demise? Indeed. A small but significant item appeared in the 10.7.4 release notes: “Improve performance when connecting to a WebDAV server.” This update is great news for WebDAV users, but bittersweet for the millions of people who cursed iDisk over the years.

Introduced as part of Apple’s “beyond the box” iTools at the 2000 Macworld Expo (see “Jobs’s Macworld Keynote Unveils Mac-Centric Internet Services,” 5 January 2000), iDisk has been almost universally derided. While iPhoto and iWeb turned publishing of photos and pages on the Internet into single-beer tasks, iDisk confounded users with frustratingly slow performance. Additional services, such as Backup and Sharing, were layered on over the years, but the performance issues remained. The Finder was prone to spinlock if an iDisk was mounted, and its read and write speeds left one pondering sneakernet fondly.

Apple’s support document, “iDisk Performs Slowly” attempted to document and elucidate the reasons why iDisk might be slow. While this document was welcome, iDisk just suffered in silence, largely ignored by users and (apparently) Apple alike. Even worse, services such as Dropbox demonstrated that cloud-based storage could work very, very well.

With this in mind, you might be wondering, Fair Reader, how it is that I come to praise iDisk. There’s the rub: the fault was never in iDisk’s cloud storage service. Nay, the fault was in Apple’s client software.

Apple didn’t talk about it much, but iDisk is an implementation of the WebDAV protocol. WebDAV is, to quote its creators, “a set of extensions to the HTTP protocol which allows users to collaboratively edit and manage files on remote Web servers.” Put simply, any WebDAV client can connect to any WebDAV server and treat it like a run-of-the-mill file server. Many Web servers run the DAV extensions, and many authoring tools (such as Dreamweaver and Coda) can access and update files on those servers.

When you choose iDisk from the Finder’s Go menu, the Finder leverages mount_webdav and webdavfs to mount the iDisk resource as a disk volume. The Finder has thus functioned as a WebDAV client since Mac OS X 10.0; it has also been able to mount non-iDisk WebDAV resources. Where I work in higher education, this capability has been relied on for years as a mechanism for providing standards-based, centrally managed file services. Universities use a variety of software systems to provide these services, but for years our Mac users have either suffered or sought solace from third party clients such as Cyberduck, Transmit,
and Interarchy. (Windows and Linux users relied on those systems’ built-in tools.)

In early 2011, my colleague Ian Crew at UC Berkeley sought to rectify the matter. He wrote an incredibly detailed analysis of the Finder’s WebDAV usage, including packet counts, protocol metrics, and speeds, and filed a high-level support ticket with Apple. Others (including myself) had filed bugs against the Finder’s WebDAV client in the past, but for reasons known only to Apple, Ian’s ticket got attention. Ideas and analysis were passed back and forth, benchmarks were performed, and ultimately Apple coded changes into the WebDAV client. According to Ian’s writeup, these changes improve WebDAV performance by about two-and-a-half times, and make
WebDAV clients more reliable and stable. Ultimately, the changes were issued in the Mac OS X 10.7.4 update.

So rejoice, iDisk users! Until 30 June 2012 you can enjoy iDisk with the speed and responsiveness we’d always hoped it would provide. iDisk took a bad rap for performance; it’s a pity that the fault lay with the Mac’s client implementation. At least everyone else using WebDAV will now reap the benefits of Ian Crew’s efforts.

[Andrew Laurence is a server administrator at the University of California, Irvine.]

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