ATA 4K sector issues

[Thiago Damas]

  I tried with gpart, gpt scheme, begining in all block alignments possible,
34, 35, 36, 37, 38, 39 etc
  Even 64
  gpart create -s gpt ad4
  gpart add -s 64 -t freebsd-zfs ad4

  With UFS, I previouly did some tests (in portuguese):

Particao sem alinhar inicio
=>        34  1953525101  ad4  GPT  (932G)
          34  1953525101    1  freebsd-ufs  (932G)

newfs -U (padrao -f 2048 -b 16384)
# time tar xfj
/install/releases/i386/8.0-RELEASE/8.0-RELEASE/ports/ports.tgz
2.342u 5.013s 20:35.65 0.5%    64+1091k 6623+2734io 0pf+0w

newfs -U -f 4096 -b 32768
# time tar xfj
/install/releases/i386/8.0-RELEASE/8.0-RELEASE/ports/ports.tgz
2.590u 5.263s 22:06.32 0.5%    63+1087k 10911+1676io 0pf+0w


Particao alinhada em multiplos de 4096 bytes (blocos logicos de 512
bytes, entao, multiplo de 8 blocos)
=>        34  1953525101  ad4  GPT  (932G)
          34          30       - free -  (15K)
          64  1953525071    1  freebsd-ufs  (932G)

newfs -U (padrao -f 2048 -b 16384)
# time tar xfj
/install/releases/i386/8.0-RELEASE/8.0-RELEASE/ports/ports.tgz
2.392u 5.000s 10:24.15 1.1%    64+1095k 8375+2735io 0pf+0w

newfs -U -f 4096 -b 32768
# time tar xfj
/install/releases/i386/8.0-RELEASE/8.0-RELEASE/ports/ports.tgz
2.547u 5.567s 1:25.50 9.4%    64+1088k 11880+1755io 0pf+0w



On Wed, Mar 17, 2010 at 3:12 PM, Olivier Smedts <olivier at gid0.org> wrote:

> 2010/3/17 Thiago Damas <tdamas at gmail.com>:
> >  I had problem with ZFS.
> >  With gnop -S 4096, it works well on /dev/ad{a}X.nop; but I decided to
> not
> > use those disks.
>
> So maybe this was not a ZFS problem but a partition misalignment problem ?
>
> On a properly aligned partition with a physical sector size of 4KB and
> a logical sector size of 512 bytes, will ZFS try to use blocksizes of
> less than 4KB ? Blocksize in ZFS seems to be dynamic (at least when
> not told to use a fixed blocksize), but I didn't see somewhere in the
> manpage or Sun's website which minimum blocksize ZFS would use for
> small files, and if there is a lower limit on blocksizes to use.
>
> >
> >
> > 2010/3/17 Mohacsi Janos <mohacsi at niif.hu>
> >
> >>
> >>
> >>
> >> On Wed, 17 Mar 2010, Dag-Erling Sm?rgrav wrote:
> >>
> >>  Mohacsi Janos <mohacsi at niif.hu> writes:
> >>>
> >>>> What is the situation with ATA 4K dirves in FreeBSD? Are there
> >>>> any support for them in fdisk or disklabel?
> >>>>
> >>>
> >>> Hmm, didn't we discuss this already?  All we need to do is change the
> >>> defaults in fdisk so it rounds partition offsets and sizes to a
> multiple
> >>> of 8 sectors (or 16 for future-proofing) instead of aligning them with
> >>> fictitious cylinder boundaries.  Bsdlabel, as disklabel is properly
> >>> known, already DTRT: by default, the first partition starts at offset
> >>> 16.  Just make sure you specify sizes that are divisible by 8 or 16
> >>> blocks (not an issue if you use the M or G suffixes).  Sysinstall
> >>> operates in megabytes.
> >>>
> >>
> >> Thanks for the information.
> >>
> >>
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>
>
>
> --
> Olivier Smedts                                                 _
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