FreBSD 9.1 and ZFS v28 performances

[Ronald Klop]

On Wed, 20 Mar 2013 11:45:37 +0100, Daniel Kalchev <daniel at digsys.bg>  
wrote:

>
> On 20.03.13 05:36, Davide D'Amico wrote:
>> Il 20.03.2013 02:37 Bob Friesenhahn ha scritto:
>>> On Mon, 18 Mar 2013, Steven Hartland wrote:
>>>>
>>>> Oh and another thing if this is mysql did you set the right settings
>>>> for your ZFS volume e.g.
>>>> zfs set atime=off tank
>>>> zfs create tank/mysql
>>>> zfs set recordsize=16k tank/mysql
>>>
>>> Very importantly, the recordsize should be set before first creating
>>> the database file.  The recordsize becomes a property of the file.
>>> Even if one sets it to 16k, the file will continue to use 128k if that
>>> was the setting when it was created.
>>
>> Well, after changing the recordsite property, I copied the file from an  
>> UFS partition (using cp -Rp): this should use recordsize=16k, right?
>
> Perhaps, if you delete the file, or preferably the entire ZFS dataset  
> first. Copying an file over another existing, does not change anything  
> with the destination file except it's contents and modification times.
> As is always with changing settings, it is safer to just create the  
> entire data set from scratch, with the new settings.
>
> Daniel

ZFS never overwrites contents of a files. It always allocates new blocks.