Re: 2.4.0: Raw devices ?

[Douglas Gilbert <dougg@torque.net>]

Meino Cramer wrote:
> short question: How cabn I activate/where can I find the raw devices
> often described as /dev/raw[12]* in/with kernel linux-2.4.0.

There doesn't seem to be any config option for raw
devices in lk 2.4.0 , they are just there. However
the raw (8) utility expects them in a different place
from where Documentation/devices.txt currently says 
they are. You may have to set up these char devices:

$ ls -l /dev/rawctl 
crw-r--r--    1 root     root     162,   0 Jan 13 05:12 /dev/rawctl

$ ls -l /dev/raw/*  
crw-r--r--    1 root     root     162,   1 Jan 13 05:12 /dev/raw/raw1
crw-r--r--    1 root     root     162,   2 Jan 13 05:12 /dev/raw/raw2
crw-r--r--    1 root     root     162,   3 Jan 13 05:12 /dev/raw/raw3
crw-r--r--    1 root     root     162,   4 Jan 13 05:12 /dev/raw/raw4
etc.

Recent versions of dd meet the alignment requirements
of raw devices as does lmdd (from the lmbench package).
I have done some timings of disk to disk copies using
raw devices compared to other devices. See:
http://www.torque.net/sg/fst_copy.html

> And where can I find the "raw" utility...

In both RH 6.2 and 7.0 the raw (8) utility is in the 
util-linux package (RH have applied a "raw" patch for 
those two lk 2.2 versions). Read man (8) raw to find 
out how to bind a raw device to an existing block device.
Example:
$ raw /dev/raw/raw1 /dev/sda3

Doug Gilbert

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