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.