Full Discussion: Difference DSK RDSK
Special Forums Hardware Filesystems, Disks and Memory Difference DSK RDSK Post 21413 by Perderabo on Thursday 16th of May 2002 07:30:59 AM
When a process sends requests to a rdsk type special file, it is talking directly to the driver. A read or a write goes directly to or from device. Reads and writes must be aligned on DEV_BSIZE boundaries or the results are undefined.

When a process sends requests to a dsk type special file, it is talking to high level os routines. A read or write goes to or from the buffer cache. If needed, the os will read new data into the buffer cache. There are no alignment restrictions. You can read or write any collection of bytes anywhere on the device. The os will send aligned requests to the driver, but this is hidden from the process. I/O requests that arise from accesses to a dsk type special file enter the driver via its strategy entry point, not the read and write entry points. The driver may resequence the requests to optimize overall performance.
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dad(7D) 							      Devices								   dad(7D)

dad - driver for IDE disk devices SYNOPSIS
dad@ target,lun:partition DESCRIPTION
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/dev/dsk/cntndnsn block files /dev/rdsk/cntndnsn raw files where: cn controller n tn IDE target id n (0-3) dn Always 0. sn partition n (0-7) The target ide numbers are assigned as: 0 Master disk on Primary channel. 1 Slave disk on Primary channel. 2 Master disk on Secondary channel 3 Slave disk on Secondary channel. IOCTLS
Refer to dkio(7I). ERRORS
EACCES Permission denied. EBUSY The partition was opened exclusively by another thread. EFAULT Argument was a bad address. EINVAL Invalid argument. EIO I/O error occurred. ENOTTY The device does not support the requested ioctl function. ENXIO The device did not exist during opening. EROFS The device is a read-only device. SEE ALSO
format(1M), mount(1M), lseek(2), read(2), write(2), driver.conf(4), vfstab(4), dkio(7I) X3T10 ATA-4 specifications. DIAGNOSTICS
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