Advanced Format Drive ?

[Arthur Chance]

On 11/13/12 06:30, Polytropon wrote:
> On Mon, 12 Nov 2012 22:14:11 -0800, Ronald F. Guilmette wrote:
>> Which "partitions" need to be aligned to the 4KB boundaries?
>> The FreeBSD ones, the MBR ones, or both?
>
> The partitions, all of them. :-)
>
> For MBR partitions, the "DOS primary partitions", which are
> slices, you typically only need one if you want to stay in
> compatibility mode. For dedicated mode, you don't need it.
>
> The slice typically starts in sector 63 and occupies the
> space until the end of the device.
>
> The partitions within the slice should have sizes of
> multiples of 1 MB or 1 GB (which makes them multiples
> of 4k easily).
>
> See:
> http://www.freebsd.org/doc/handbook/bsdinstall-partitioning.html
>
> Even though the handbook elaborates on the GPT approach, it
> will work with traditional disklabel partitioning too.
>
> Note that 4k = 8 x 512 byte, and so 64 sectors would be a
> good alignment "grid", while 63 sectors is not. That implies
> that in case you use fdisk to create a slice holding your
> partitions, try to make it start at sector 64 (63 would
> have been the default).
>
> After that, use bsdlabel to create the partitions inside
> the slice as you want. Make them multiples of 1M or 1G,
> that should be no big deal because disks are big and cheap
> today. :-)
>
> You can then easily use newfs with the -f parameter:
>
> 	newfs -U -f 4096 <device>
>
> This will make sure the proper fragment size will be applied
> upon formatting the created partitions.
>
> Also see:
> http://www.wonkity.com/~wblock/docs/html/disksetup.html
>
> As I have limited experience, anyone having more practical
> experience with this matter is welcome to comment. :-)

According to the manual as of 9.0-RELEASE the default fragment and block 
sizes for newfs are 4k and 32k, so provided your partitions/slices are 
4k aligned everything Should Just Work. Before 9.0 fragments and blocks 
were 2k and 16k which doesn't play so well with 4k drives.