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Tape Devices in Solaris

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Yes, people out there are still using tape – and in fact in certain situations tape still has many advantages over disk backup or site replication. One of the many quirks with Solaris is how tape devices are addressed, so in this post I’m going to quickly cover the options.

Solaris tape devices all live under /dev/rmt, where rmt stands for Raw Magnetic Tape device.

First tape device name: /dev/rmt/0
Second tape device name: /dev/rmt/1

Each tape device also has special characters added after it to specify density and the characteristics of the drive that you want to use.

So the actual format you’d use to address a drive would be /dev/rmt/XY, where:

  • X is tape drive number such as 0, 1 etc.
  • Y can be any one of following
    • l – Low density
    • m – Medium density
    • h – High density
    • u – Ultra density
    • c – Compressed density
    • n – No rewinding

It’s actually pretty straightforward. If you want to use tar to backup to your first tape drive, using compressing, and not rewinding the media afterwards (so you can append to the backup), you’d use the device /dev/rmt/0cn

On top of this, Solaris comes with a utility called mt, which is used to carry out some simple tape operations.

mt takes the -f option to specific which device it should talk to, and it then mainly used for these three options:

  1. Rewinding a tape
    # mt –f /dev/rmt/0 rewind
    
  2. Display the status of a tape drive
    # mt –f /dev/rmt/0 status
    
  3. Retensioning a tape
    # mt –f /dev/rmt/0 retension
    

Most people will have some sort of front end software to handle their tape backups – Oracle RMAN, Networker, Netbackup or similar – but if you need to do a quick test, or are just using tar or another backup utility, then this post should point you in the right direction.

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