🚀 go-pugleaf

> 	Some people say that 'extent-based' file systems are inherently
> faster than unix's.

Depends on the file size. If by an 'extent based' system you mean a linked
list of large extents, as opposed to a tree of small extents which is what
the UNIX file system actually is (an extent is just a single indirect block,
in UNIX terminology), then for small (1-2 extent) files UNIX will be slower.
Once you have more than 2 extents you're going to be doing 3 indirects with
your extent based system anyway, whereas UNIX will still be accessing the
first or second indirect block (I'm not sure of the terminology):

Assuming buffering and equal blocksize:

N = #ptrs/block

UNIX:	INODE
	10 * ^block
	1* ^indirect block (<n> of ^block)
	1* ^double indirect block (<n> of ^indirect block)
	1* ^triple indirect block (<n> of ^double indirect block)

E-SYS:	EXTENT
	<n>-1 * ^block
	1* ^EXTENT

So the first 10 blocks take 1 indirect in each. The next <n>-11 blocks
take 1 indirect in your extent system, 2 in UNIX. The next 9 blocks
take 2 indirects in each. Then there are another <n>-11 with 3 indirects.
After that UNIX is ahead... 3 indirects for UNIX, 4 or more for extents.

That may be screwed up somewhere, but by inspection you should be able to
see that after the third extent UNIX is ahead.

I wonder if that's why this damn IBM-PC is seeking all over the place? Nah.
My files aren't that big.
-- 
	Peter (Made in Australia) da Silva
		UUCP: ...!shell!neuro1!{hyd-ptd,baylor,datafac}!peter
		MCI: PDASILVA; CIS: 70216,1076