ZFS installs on HD with 4k physical blocks without any warning as on 512 block size device

[Peter Jeremy]

On 2011-Aug-22 12:45:08 +0200, Ivan Voras <ivoras at freebsd.org> wrote:
>It would be suboptimal but only for the slight waste of space that would 
>have otherwise been reclaimed if the block or fragment size remained 512 
>or 2K. This waste of space is insignificant for the vast majority of 
>users and there are no performance penalties, so it seems that switching 
>to 4K sectors by default for all file systems would actually be a good idea.

This is heavily dependent on the size distribution.  I can't quickly
check for ZFS but I've done some quick checks on UFS.  The following
are sizes in MB for my copies of the listed trees with different UFS
frag size.  These include directories but not indirect blocks:

  1b  512b  1024b  2048b  4096b
4430  4511  4631   4875   5457  /usr/ncvs
4910  5027  5181   5499   6133  Old FreeBSD SVN repo
 299   370   485    733   1252  /usr/ports cheched out from CVS
 467   485   509    557    656  /usr/src 8-stable checkout from CVS

Note that the ports tree grew by 50% going from 1K to 2K frags and
will grow by another 70% going to 4KB frags.  Similar issues will
be seen when you have lots of small file.

-- 
Peter Jeremy
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