efs

[David A Higgen]

> Can anyone tell me what an "Extent File System" is (compared to a "normal"
> Unix System V file system).  I see it mentioned in nearly every SGI document
> but I haven't been able to find and explaination of what the benefits are.
> 
> Thanks!  --Pete Poorman

'man fs' will give you some basic information.
There are also extensive explanatory comments in several of the 
include/sys/fs header files. Particularly efs_fs.h and efs_sb.h.

The main benefit over a sysV filesystem is speed: space for files is
allocated not on a one-by-one block basis but in chunks ("extents") 
of contiguous blocks which may be up to 248 blocks in size. So I/O
happens in larger, faster, units.


			Dave Higgen