ZFS installs on HD with 4k physical blocks without any warning as on 512 block size device

Pieter de Goeje pdegoeje at service2media.com
Fri Aug 19 12:17:55 UTC 2011

On Friday, August 19, 2011 12:15:30 PM Tom Evans wrote:
> On Thu, Aug 18, 2011 at 6:50 PM, Yuri <yuri at rawbw.com> wrote:
> > Some latest hard drives have logical sectors of 512 byte when they
> > actually have 4k physical sectors. Here is the document describing what
> > to do in such case:
> > http://ivoras.net/blog/tree/2011-01-01.freebsd-on-4k-sector-drives.html .
> > For UFS: newfs -U -f 4096 /dev/da0
> > For ZFS: gnop create -S 4096 /dev/da0 && zpool create data /dev/da0.nop
> > 
> > I am sure most people just install such hard drive without doing this and
> > potentially get suboptimal performance since they aren't aware about
> > this. Shouldn't UFS and ZFS drivers be able to either read the right
> > sector size from the underlying device or at least issue a warning?
> > 
> > Yuri
> The device never reports the actual sector size, so unless FreeBSD
> keeps a database of 4k sector hard drives that report as 512 byte
> sector hard drives, there is nothing that can be done.
> Cheers
> Tom

In -current at least there is a quirk table for these drives - the stripe size 
is set to 4K. Other tools use this size to align stuff on. Also, the default 
fragment size of UFS was increased to 4K.

- Pieter

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