ATA 4K sector issues

[Olivier Smedts]

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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