On 06.12.2010 23:22, Ivan Voras wrote:
On 6 December 2010 22:16, Bruce Cran<br...@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".
It is only question of abstraction. As soon as any our disk device is
GEOM abstraction - don't see reason why parameters should be specific.
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".
`camcontrol identify` directly requests IDENTIFY data and parses them.
There is nobody between it and the device. To see what GEOM receives
from the disk driver use diskinfo.
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.
There could be a long list of different "stripesize" sources. It is not
a task of the partitioning tool or file system to know all of them. As I
have described in previous email - only size matters.
# camcontrol identify /dev/ada1
...
device model WDC WD10EARS-00Z5B1
...
sector size logical 512, physical 512, offset 0
Agreed. Some drives lie.
"Everybody lies". :) If Linux example was taken from page I've seen - it
was external WD USB storage somehow reporting that physical sector size,
not the disk itself. I haven't seen proper reporting in any WD drive yet
(started to think about adding quirk at ada driver). Now waiting for
Seagate 4K disks reports to check how bad things are.
--
Alexander Motin
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