Re: ZFS installs on HD with 4k physical blocks without any warni

On 23/08/2011 03:23, Peter Jeremy wrote:
> On 2011-Aug-22 12:45:08 +0200, Ivan Voras<ivoras@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.

I agree but there are at least two things going for making the increase 
anyway:

1) 2 TB drives cost $80
2) Where the space is really important, the person in charge usually 
knows it and can choose a non-default size like 512b fragments.

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