The original question was:
What is the meaning of the values in bdev and cdev fields appearing in
subdisk and volume reports (volprint vl/sl).
Hier the answer of Dr. Tom Blinn:
If you look the /dev directory on your system, you will find a number of
files, and if you look at them with ls -l you will see that some of them
have a "c" type and some have a "b" type, and where for a regular file you
would see the file size, for these files you see a pair of numbers.
These special files are "character" and "block" device files. The name you
see in the volprint output of "bdev" means that the disk in question (such
as /dev/rz17g in your example) corresponds to block device 8,33798. The "8"
is known as the 'major' number and indexes into a table called the block
device switch (bdevsw) in the kernel to associate references to the device
with a particular device driver that implements the block i/o model. The
rest of the number (the 'minor' number) is interpreted by the device driver
in ways that are determined by the driver itself. For instance, for block
disk interfaces, the "rz" number (17 in your example) and partition number
("g" in your example) as well as other things are encoded in the minor part
of the device number. "character" device numbers work the same way, but are
indexed into the character device switch table (cdevsw) and like the case of
block devices, the minor number is interpreted by the device driver.
For your usrvol, if you were to look at the file /dev/vol/rootdg/usrvol with
ls -l, you should find that the major number is 40 and the minor number is 7
but I don't know whether it will show up as a block or character device.
None of this has anything to do with blocking or buffering, or performance.
If you have performance problems, get out the tuning guide and study it.
Thanks a lot to:
Pierre Wendling
Lucien Hercaud
Dr. Tom Blinn
alan
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Received on Fri May 29 1998 - 17:52:15 NZST