Hallo,
many thanks to Whitney Latta and Alan. This time i can't summarize all
items as well as both of them did it in their explanations, so i simply
attach both mails!
Whitney:
The warning you received when you did the newfs(8) on the disk was the
result of having the wrong "disktype" when the label was written to
disk. When you wroet the label, you explicitly designated "rz28" as the
disk type. When using this syntax, the label is taken from the entry in
the cam_data.c structures for that device type specifically (whether the
disk in question really is a rz28 or not!)
When labeling disks and also when newfs'ing UFS filesystems, it is far
preferable to simply use the device driver to "build" the label
dynamically. So, use the "unknown" scsi disk type "rzxx" (or any other
"unknown" string for the device type) in the disklabel syntax:
Example: disklabel -rw rz2 rzxx
The above example will go to the device driver and extract the
appropriate disk geometry information and build a default label on disk.
This works for any disk type, even non-Digital/Compaq disks. Once you
have a default label on the disk, it can be modified very easily to get
any size partitioning schem. After running the above label command, read
the label back (disklabel -r rz2), and you will see the correct "disk
type" in the second entry of the label.
The cam_data tables, and the /etc/disktab file (for newfs) should only
be used any more when a "very specific" disk partitioning scheme is
required, and you don't want to do it manually for each and every disk.
Alan:
The first warning simply means that the geometry reported by
the drive when the label was written disagrees with the value
in /etc/disktab. Neither value is particulary correct, since
most modern SCSI drives (and all the RZ28 family) use zone
based recording and have many different values of the number
of sectors per track. This is nothing to worry about.
I think newfs likes to make file systems end on cylinder
group (or perhaps just cylinder) boundaries. It has no
easy way of knowing whether the partition starts on a
cylinder boundary, so it assumes it does. The end of the
usable space also has to be a multiple of 8 KB. For disks
with multiples of 16 tracks (the RZ28 is one), this requirement
is relatively easy. Typcially the wasted space is small
percentage of the total space, but you can size the partitions
not to waste the space for most partitions. Once you get to
the end of the disk it may not be possible to waste some in
the last partition because the disk simply isn't the right
size.
mit freundlichen Grüßen
Reimund Willig
willig.reimund_at_gdr.de
Received on Mon Jul 27 1998 - 09:05:55 NZST