physical disk access
Thu Dec 30 13:28:00 GMT 1999
I am doing disk testing of physical devices on NT. Under NT, I can
access the physical disks using names of the form "\\.\..." where the
... can be a drive letter (including the colon) or a name like
"physicaldrive2". The physical drive scheme numbers the drives starting
at 0, in sequence for all drives found.
I wanted to use dd to verify disk sizes on reads and writes, so I used
the following two commands:
dd if='\\.\F:' of=/dev/null bs=1024k
zero | dd of='\\.\F:' bs=1024k
where the command zero just generates null bytes on standard out.
The first command runs fine and reports the expected size (300 MB). The
second fails with "dd: \\.\F:: Invalid argument". I wrote a quick
program in C to check error conditions/permissions, using
open("\\\\.\\F:", O_RDWR). The program can write to this device without
I would have expected dd to work for both in and out operations under
these circumstances. Any idea why it didn't?
I am running the Cygwin 1.0 environment from the CD, no updates.
Staff Software Quality Engineer
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