Use of fragmented and compressed file systems
JFS supports fragmented and compressed file systems. Both types of file systems save
disk space by allowing a logical block to be stored on the disk in units or fragments
smaller than the full block size of 4096 bytes. In a fragmented file system, only the last
logical blocks of files no larger than 32 KB are stored in this manner, so that fragment
support is only beneficial for the file systems containing numerous small files. Data
compression however, allows all logical blocks of any sized file to be stored as one or
more contiguous fragments. On average, data compression saves disk space by about
a factor of 2. JFS2 does not support file system compression.