The Advanced File System provides rapid crash recovery, high performance, and a flexible structure that enables you to manage your file system while it is on line. An optional set of utilities is available for AdvFS that expands the capabilities of the file system. This release includes all of the patches I have been sent against the 0.6x defrags. Please let me know if there are any other changes outstanding. A bug fixed in valid-check of filesystem.
Commercial products exist to handle defragmentation.
Out of contiguous space Allocations for indirect extents require contiguous space, but only up to 32 blocks. Sounds like a large file is trying to grow in a very fragmented file system. However if clearing up the fragmentation is more important it's perfectly safe to run fsr no matter how busy the file system or system.