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Date:      Tue, 3 Jan 2012 19:34:07 -0600 (CST)
From:      Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
To:        Jeremy Chadwick <freebsd@jdc.parodius.com>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: ZFS With Gpart partitions
Message-ID:  <alpine.GSO.2.01.1201031928550.15666@freddy.simplesystems.org>
In-Reply-To: <20120103235108.GA25691@icarus.home.lan>
References:  <4F003EB8.6080006@dannysplace.net> <CALfReyfvOCMpBdndf7UYydmGnUqt2cBYWdhYXaOANbQ_CFHoVA@mail.gmail.com> <4F02FC42.1040103@dannysplace.net> <4F0311F2.7050209@brockmann-consult.de> <4F0312DF.8050004@brockmann-consult.de> <20120103162428.GA18661@icarus.home.lan> <CALfReyc11ZriFPZmm15YwS5VeA1P4Epub1vyZM%2BfC8X2X0_mHw@mail.gmail.com> <20120103235108.GA25691@icarus.home.lan>

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On Tue, 3 Jan 2012, Jeremy Chadwick wrote:
>>
>> There has been.quite a bit of discussion on this already and I think the
>> safest way is to always 4k align as this works fine on.both drive types
>
> Agreed.  The question is why FreeBSD isn't using those defaults in its
> installer.

As it happens, 4k alignment increases space consumption.  A zfs 
metadata element which previously consumed just 512 bytes (really at 
least 1024 bytes due to redundancy) would then consume 4k bytes (or 8K 
bytes due to redundancy).  Users with large numbers of small files 
have definitely noticed the loss of disk space.

Users with 15K RPM SAS drives are likely to have different 
requirements than users with large SATA drives.

The installer should obtain the requirements from the user and provide 
suitable warnings about the negative behavior which may occur from 
either option.

Bob
-- 
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/



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