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Conference stkhlm::magtape

Title:	MAGNETIC TAPEDRIVES

Moderator:	STKHLM::GJOHNSSON

Created:	Mon Sep 21 1987
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	3775
Total number of notes:	13147

3748.0. "RW532 backup problem" by HGOSPS::MASCOTTANG () Wed May 14 1997 09:40

  My customer buys a RW532 optical drive, he read the specifiction, the drive
can backup data up to 0.47 megabytes, but he uses the on-line image backup
in a ALPHA 4000/233 system, the RW532 can only backup 0.15 megabytes per second.
The drive is connected on a SCSI bus on a ALPHA 4000/233 system. The system is
running VMS V6.2. 

     My customer would like to ask the following questions for my customer. 
Any advice should be appreciated.

1) Under circumstance the RW532 can backup 0.47 megabytes ?
2) Would any configuration problem cause the backup speed only 1/3 of maximum
   speed ?
3) Can we have other method to tune the tape drive faster ?

T.R Title User Personal
Name Date Lines

3748.1 LEFTY::CWILLIAMS CD or not CD, that's the question Wed May 14 1997 15:35 26

T.R	Title	User	Personal Name	Date	Lines
3748.1		LEFTY::CWILLIAMS	CD or not CD, that's the question	`Wed May 14 1997 15:35`	26
	The RW532 is an optical Library, not an optical drive, and certainly not a tape drive. It requires control SW to run both the library and the drive. The specs you are quoting seem to be hardware specs, not system specs, plus you are missing a lot of required information to figure this out. Remember also that backup from disk to disk is usually much slower than backup from disk to tape, as the directory entries and allocation tables have to be constantly updated. The RW5xx series optical systems are disks, and suffer from this system restriction. Your actual data transfer rate is higher than you think it is, but there is more overhead, which cuts the rate of user data backup. What SW is being used to control the jukebox? Version? What density media is being used? What controller is being used to drive the jukebox? What else is on the bus? How much memory in the system? Has backup been tuned, as the backup docs recommend? Bottom line is that the customer is probably using it for an application that it was not really intended for. Chris

    The RW532 is an optical Library, not an optical drive, and certainly
    not a tape drive. It requires control SW to run both the library and
    the drive. The specs you are quoting seem to be hardware specs, not
    system specs, plus you are missing a lot of required information to
    figure this out. 
    
    Remember also that backup from disk to disk is usually much slower than
    backup from disk to tape, as the directory entries and allocation
    tables have to be constantly updated. The RW5xx series optical systems
    are disks, and suffer from this system restriction. Your actual data
    transfer rate is higher than you think it is, but there is more
    overhead, which cuts the rate of user data backup.
    
    What SW is being used to control the jukebox? Version?
    What density media is being used?
    What controller is being used to drive the jukebox?
    What else is on the bus?
    How much memory in the system? 
    Has backup been tuned, as the backup docs recommend?
    
    Bottom line is that the customer is probably using it for an
    application that it was not really intended for.
    
    Chris