Writing contigiously to UFS2?

Rick C. Petty rick-freebsd at kiwi-computer.com
Tue Sep 25 20:19:03 PDT 2007

On Sat, Sep 22, 2007 at 04:10:19AM +1000, Bruce Evans wrote:
> of disk can be mapped.  I get 180MB in practice, with an inode bitmap
> size of only 3K, so there is not much to be gained by tuning -i but

I disagree.  There is much to be gained by tuning -i: 224.50 MB per CG vs.
183.77 MB..  that's a 22% difference.

However, the biggest gain by tuning -i is the loss of extra (unused)
inodes.  Care should be used with the -i option-- running out of inodes
when you have gigs of free space could be very frustrating.  But I newfs
all my volumes knowing an approximate inode density based on
already-existing files and a minor fudge factor.  The only time I ran out
of inodes with this method was due to a calculation error on my part.

> more to be gained by tuning -b and -f (several doublings are reasonable).

I completely agree with this.  It's unfortunate that newfs doesn't scale
the defaults here based on the device size.  Before someone dives in and
commits any adjustments, I hope they do sufficient testing and post their
results on this mailing list.

-- Rick C. Petty

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