mkfs and disk performance

[Mr. Gircys]

I recently had to add inodes to my news directory, and in doing
so, discovered that the system disk performance is now roughly
twice as slow as compared to the pre-inode-add file system (based
on timing expire/rnews execution).

I suspect the problem is that I used default values for "gap blocks/cyl"
parameters. Does anyone have suggestions on how to choose proper values 
for gap & blks/cyl.

My system has a 140meg scsi disk/adaptec1452 cont; the default values are
gap=9 blks/cyl=400; Esix V.3.2 Unix OS - and I've called Esix tech support
...

Any insight is welcome.