Formats
DirectoryStorage keeps data using one file per revision per object. Each file is stored in a directory. The precise arrangement of files into subdirectories is known as a format. The following formats are available:
bushy
If you are using a filesystem that is inefficient with directories containing larger than a few hundred items. This is optimal for most conventional filesystems, such as ext2 on linux. In this format each object is given its own directory nested inside 8 levels of subdirectory. Each revision of an object has its own file in that directory.
chunky
If you are using a filesystem that is most efficient with directories containing tens of thousands of subdirectories, or hundreds of thousands of files. This is optimal for filesystems such as reiser3 or JFS on linux. In this format, one subdirectory is shared by up to 65000 objects. That subdirectory is nested inside 4 levels of subdirectory.
lawn
If you are using a filesystem that is efficient with huge directories. Each object gets its own directory directly off the database home directory. Only a few filesystems support a suitably large number of subdirectories in a single subdirectory - XFS, NTFS, possibly others. I would be interested in any tests using this format on one of these filesystems. If you are using one of these filesystems but dont have time to perform tests then I recommend you use 'chunky'.
flat
Everything goes in one big directory. This is handy when studying how DirectoryStorage works because it gives the least complicated directory layout. It is probably not suitable for production use.
bushy4
This format is no longer supported.