Why at least 4 cylinder groups?

[Rodney W. Grimes]

> Hello.
> 
> In an embedded system I am having a rather
> small (static) ram disk of about 1.5MB,
> formatted as UFS(1).
> 
> Under FreeBSD 4 dumpfs shows me there is
> 1 cylinder group.
> 
> Under FreeBSD 9 and 10 I see 4 cylinder groups.
> 
> 4 is hard coded as the minimum value in ufs/ffs/fs.h. Why?

I beleive this constant only applies to UFS version 2, newfs -O 2,
which is default in FreeBSD 9 and 10.

> Is there any technical reason not to have less
> than 4 cylinder groups?

Probably on a UFS2 file system yes, but as far as I can
see not on a UFS1 file system.

> For my application the wasted 188KB make a difference.

Try:
	newfs -O 1

> Thank you,
> Norbert Koch

-- 
Rod Grimes                                                 rgrimes at freebsd.org