Apple released Xsan 1.2 today, and a full description of the upgrade, available as four different software updates (!), is available in this support article. The downloads themselves are available either via Software Update or as standalone installers. Additional migration information is available in this support article, and additional information on working within the 2 TB LUN size limit is available in this support article. So much to digest -- don't forget to post your thoughts on the improvements, as well as your experiences with the upgrade, in our Xsanity forums.

For most of you, defragmentation has become a regular practice in the administration of your Xsan volume. At some point, either capture files, or more commonly, render files are becoming so fragmented across the breadth of the storage that their playback predictably yields dropped frames.

The solution, of course, is to run the snfsdefrag utilitity, found in /Library/Filesystems/Xsan/bin, or to use the handy Xsanity Defrag program, Xsanity's cocoa wrapper of the same utility, in order to address the issue. [Ed. Note: Our Xsanity Defrag is getting old and creaky, and we do not currently recommend it!]

The snfsdefrag utility, used in its simplest form, gathers all the fragments of a given file (called “extents” by the utility) and places them in a section of the free space of the storage in one continuous chunk. The “virgin” territory that it usually seeks out in order to do this is the “far end” of the storage pool, which would usually not fill up until the storage pool itself reached its maximum capacity.

Apple today announced new PowerMacs. The architecture new features two Gigabit Ethernet ports on the motherboard, a 100% increase, which is great for Xsan. The PCI slots are now PCI Express, which is not backwards compatible with PCI or PCI-X. So you'll need new Fibre Channel HBAs for these new Macs. Apple says they are shipping their PCI Express HBA in 3-4 weeks.

Apple made 5MB of fresh meat available today for all you early adopters. Get your hands on Xserve RAID Admin Tools 1.5 Update via either Software Update or the standalone installer. Along with a pretty fair list of new features and a few fibre channel compatibility updates, the release brings some new procedures for adding and moving drives and arrays, as well as for replacing controller modules. The update is recommended for all Xserve RAID users; still, spend an appropriate amount of time with the README -- wouldn't want to hurt yourself out there on that cutting edge.

UPDATE: The premonition about fragmentation was correct. The morning after the pruning was filled with dropped frames. Be careful using this operation on volumes used for video storage.

When you write files to an Xsan volume, an application can ask the metadata controller to preallocate a certain number of blocks on the filesystem. But you may not end up using all those blocks for data. To quickly recover that allocated, but unused, space, type this command:

sudo snfsdefrag -rvp /Volumes/XSAN

Instead of "XSAN" type the name of your Xsan volume. On one 14 TB volume that was a bit less than half full, I recovered 700 GB. (Of course, that space is going to be pretty fragmented.)

EMC Dantz tiptoes into support for Xsan this week with the release of Retrospect 6.1 for Mac, a free update for Retrospect 6 users. The release notes convey a whole laundry list of caveats, though — don't install it on the SAN itself, forget about creation dates, forget about Access Control Lists, forget about subvolumes, expect some compare errors. Still, promising, and I'm sure we'll give it a try here ... meanwhile I'd welcome any backup stories from those of you using competing products, successful or otherwise.

Apple has released the Xsan Tuner application for testing and tuning Xsan installations.

About the Xsan Tuner Application

The Xsan Tuner application is used to test the data and video transfer capabilities of your storage area network and it’s Xsan volumes. Xsan Tuner can simulate both standard UNIX reads and writes as well as Final Cut Pro video reads and writes for a variety of common video formats.

Use Xsan Tuner to see if your SAN can handle planned workloads before you put it into production use. An Xsan Tuning Guide is provided along with the application to help understand the Xsan Tuner results as well as provide configuration suggestions to optimize your SAN performance.

To use the Xsan Tuner application, you need the following:

• Mac OS X or Mac OS X Server v10.4.2 or later
• Xsan 1.1 or later