Fast Filesystem defaults

[System Mangler]

>   If you have one inode per 2K of data space, then it doesn't matter
>   how many blocks/cyl-group; more blocks just means more inodes.  So
>   how does having rp07s make any difference?

Mkfs cannot allocate more than MAXIPG (=2048) inodes per cylinder
group.	With 16 cylinders per group, this limit comes into play on
any drive with more than 512 sectors per cylinder.
	RM05	19 x 32 = 608	    effective -i value = 2432
	RA81	14 x 51 = 714	    effective -i value = 2856
	Eagle	20 x 48 = 960	    effective -i value = 3840
	2298	16 x 68 = 1088	    effective -i value = 4352
	9775	40 x 32 = 1280	    effective -i value = 5120
	9771	16 x 84 = 1344	    effective -i value = 5376
	RP07	50 x 32 = 1600	    effective -i value = 6400
Thus on a big disk, you have to decrease the number of cylinder
groups if you need lots of inodes.  Mkfs doesn't tell you this,
though.

So you see that the newfs default for "-i" is usually not only
unrealistic, but a false promise as well.  For the disks most
people use (Eagle or RA81), -i 4096 is a more truthful value.

My point was that newfs, which is supposedly a ``friendly''
preprocessor for mkfs's long argument list, ought to compute
things like -i, -b, -f, -c, and maybe -m from a single novice-
understandable number, the expected average file size.	Anyone
can divide the numbers from "df -i" output, or from a count of
files and megabytes on a distribution tape.  And isn't this
the figure that really determines what settings are optimal?

			Don Speck   speck at cit-vax.arpa