Orlov block allocator

The Orlov block allocator is an algorithm to define where a particular file will reside on a given file system (blockwise), so as to speed up disk operations. The Orlov block allocator is an algorithm to define where a particular file will reside on a given file system (blockwise), so as to speed up disk operations. The scheme is named after its creator Grigoriy Orlov, who first posted a brief description and implementation for OpenBSD of the technique, which was later used in the BSD Fast Filesystem kernel variants. The performance of a file system is dependent on many things; one of the crucial factors is just how that filesystem lays out files on the disk. In general, it is best to keep related items together. The Linux ext2 and ext3 filesystems, for instance, have tried to spread directories on the cylinders of the disk. Imagine setting up a system with users' home directories in /home: if all the first-level directories within /home (i.e. the home directories for numerous users) are placed next to each other, there may be no space left for the contents of those directories. User files thus end up being placed far from the directories that contain them, and performance suffers.