don rauenhorst wrote:
Frank Hofmann i woult like to know more about these changes regarding the sourcecode.
thanks donr
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See the following link
http://sunsolve.sun.com/search/document.do?assetkey=urn:cds:docid:1-21-119375-03-1
Not so long ago, disks were addressed by cylinder, head, and sector number.
The capacity of a disk could be determined by multiplying the number of
cylinders,
heads, and sectors together. Today we have pretty much stopped using CHS
addressing
only use the capacity, but there are still a few vestiges of CHS
geometry laying around.
One example is allocating partitions and slices on cylinder boundaries,
another is the
notion of cylinder groups within the UFS filesystem.
Solaris supports CHS geometry as three 16 bit fields (C:16 H:16 S:16),
but SCSI disks support different sized fields (C:24 H:8 S:16).
Until recently this was not a problem, but with today's disk sizes we
are seeing
disks use 17 or more bits of the SCSI cylinder address. When that cylinder
address is stored in a 16 bit field, we lose the most signifigant bits and
report a truncated disk size.
We still need to support applications which use geometry, with this
patch installed
we increase the number of heads or sectors and decrease the number of
cylinders
and keep all three values within the 16 bit limits.
There is a compatability issue! If a disk was originally labeled with
one geometry
we have to continue using that geometry, even if it means loss of disk
space.
If a disk is not labeled, then we are free to allocate a new geometry
and store the
new geometry in the disk label and no loss of disk capacity will occur.
If you have a disk with no data on it, then you can erase the disk
labels with
the dd command, as described in the patch.
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