svn commit: r216230 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[John Baldwin]

On Monday, December 06, 2010 4:22:35 pm Ivan Voras wrote:
> On 6 December 2010 22:16, Bruce Cran <bruce at cran.org.uk> wrote:
> > On Mon, Dec 06, 2010 at 09:31:39PM +0100, Ivan Voras wrote:
> >> For what it's worth, apparently linux has the concept of "physical"
> >> and "logical" sector sizes (possibly in addition to "stripe size"),
> >> with physical being 4096 and logical 512, for example:
> >>
> >> # hdparm -I /dev/sde | grep size
> >> Logical  Sector size:                   512 bytes
> >> Physical Sector size:                  4096 bytes
> >> device size with M = 1024*1024:     1430799 MBytes
> >> device size with M = 1000*1000:     1500301 MBytes (1500 GB)
> >
> > So do we, except they're both the same for Advanced Format drives:
> 
> There is a subtle difference here which may be important. We have the
> concepts of "sectorsize" and "stripesize".
> 
> I think camcontrol actually reports logical and physical sector sizes
> as reported by low-level drivers but currently GEOM names "logical
> sector size" as "sectorsize" and "physical sector size" as
> "stripesize".
> 
> The term "stripesize" can be overloaded to mean both the item in
> question - 4 KiB physical sector sizes and RAID stripe sizes. I think
> this situation is bad and that the two meanings should be split.

My understanding in GEOM is that the primary meaning for stripe size is for 
the RAID use case.  It is probably the 4K logical sector size that needs to 
come up with a new field, not vice versa.

-- 
John Baldwin