passthrough devices vs. named devices Post: 302202331

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Top Forums UNIX for Dummies Questions & Answers passthrough devices vs. named devices Post 302202331 by thumper on Wednesday 4th of June 2008 02:41:35 PM

06-04-2008

Registered User

passthrough devices vs. named devices

I am having trouble understanding the difference between a passthrough device and a named device and when you would use one or the other to access equipment.

As an example, we have a tape library and giving the command
"camcontrol devlist" gives the following output:

akx[22]# camcontrol devlist
<SPECTRA 215 1014> at scbus3 target 3 lun 0 (pass4,ch0)
<SONY SDX-300C 04c7> at scbus3 target 8 lun 0 (pass5,sa0)

The SPECTRA 215 is the tape library the SONY SDX is the tape drive in the library.
To address the tape library a command such as "mtx -f /dev/pass4 command" is used, however to address the tape unit then /dev/sa0 would be used as in
"/sbin/dump -0uaf /dev/sa0 /dev/da4s1e".

Could someone give me a clue on when you address a passthrough device and when you address a named device, or at point me to some documentation that might clear this up?

Thanks
Thumper

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LEARN ABOUT OPENSOLARIS

tcopy

tcopy(1)							   User Commands							  tcopy(1)

NAME

       tcopy - copy a magnetic tape

SYNOPSIS

       tcopy source [destination]

DESCRIPTION

       The  tcopy  utility copies the magnetic tape mounted on the tape drive specified by the source argument. The only assumption made about the
       contents of a tape is that there are two tape marks at the end.

       When only a source drive is specified, tcopy scans the tape, and displays information about the sizes of records and tape files. If a  des-
       tination  is  specified,  tcopy makes a copies the source tape onto the destination tape, with blocking preserved. As it copies, tcopy pro-
       duces the same output as it does when only scanning a tape.

       The tcopy utility requires the use of Berkeley-compatible device names. For example,

	 example% tcopy /dev/rmt/1b /dev/rmt/2b

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWesu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       mt(1), ioctl(2), attributes(5)

NOTES

       tcopy will only run on systems supporting an associated set of  ioctl(2) requests.

SunOS 5.11							    10 Mar 2000 							  tcopy(1)

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