block and fragment sizes with newfs

David Kelly dkelly at
Wed Apr 23 09:34:12 PDT 2003

Playing with UFS on CF (Compact Flash) cards where I'm concerned about
wear and tear, and maximum efficiency.

It would seem "newfs -b 4096 -f 512" would result in fine grained
control over each and every 512 byte block on my CF card and eliminate
writes to multiple blocks when a write to a single block would do.

The above creates a lot of "superblock backups", leading me to suspect
what I save in fragment size == block size, I lose in overhead to track
all these fragments.

The default is "-b 16384 -f 2048", which if I understand correctly means
the minimum read/write to the filesystem will be 2048 bytes?

A middle of the ground compromise is "-b 8192 -f 1024".

What's the deal?

David Kelly N4HHE, dkelly at
The human mind ordinarily operates at only ten percent of its
capacity -- the rest is overhead for the operating system.

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