Understanding tape devices

About tape devices

When you install a tape drive or tape stacker on a filer according to the tape drive manufacturer's instructions, Data ONTAP creates tape devices associated with the tape drive or stacker. A device is created for each combination of rewind and compression capability. Therefore, a tape drive or tape stacker can have several tape devices associated with it. You must specify a tape device to move, write, or read tapes.

Data ONTAP detects tape drives and tape stackers attached before or after bootup and assigns logical numbers and tape devices to them.

Kinds of tape devices

The following kinds of tape devices are available:

A local tape device on the filer that is performing a tape operation
A remote tape device on a NetApp or Solaris machine that
- Is not the machine that is performing a tape operation, but is connected through the network to a host that is performing the tape operation
- Is running the rmt protocol
- Has a trust relationship with the filer that is performing the tape operation
  Note
  You cannot use tape devices associated with tape stackers or tape libraries (medium changers) on a remote Solaris system.

Tape device name format

The format of a tape device name is as follows:

[remote_host:]rewind_type st drive_number compression_type

remote_host is optional. You specify a remote host filer if you want to use a tape drive that is attached to that host. You must follow the remote host name with a colon (:).

rewind_type is the rewind type, as shown in the following table.

Rewind type	Description
`r`	Rewind. Data ONTAP rewinds the tape after it finishes writing the tape file.
`nr`	No rewind. Data ONTAP does not rewind the tape after it finishes writing the tape file. If you want to write multiple tape files on the same tape, specify no-rewind tape device names.
`ur`	Unload/reload. You can use this only if you are performing operations on tapes in tape stackers. When you use these devices, the stacker unloads the tape when it reaches the end of a tape file, and then loads the next tape if there is one. Use this rewind type only under the following circumstances: The tape drive associated with this device is housed in a tape stacker or a medium changer that is set to stacker mode. The tape drive associated with this device is attached to a filer. Sufficient tapes for the operation that you are performing are available in the stacker tape sequence defined for this tape drive.

Rewind type

Description

r

Rewind. Data ONTAP rewinds the tape after it finishes writing the tape file.

nr

No rewind. Data ONTAP does not rewind the tape after it finishes writing the tape file. If you want to write multiple tape files on the same tape, specify no-rewind tape device names.

ur

Unload/reload. You can use this only if you are performing operations on tapes in tape stackers. When you use these devices, the stacker unloads the tape when it reaches the end of a tape file, and then loads the next tape if there is one.

Use this rewind type only under the following circumstances:

The tape drive associated with this device is housed in a tape stacker or a medium changer that is set to stacker mode.
The tape drive associated with this device is attached to a filer.
Sufficient tapes for the operation that you are performing are available in the stacker tape sequence defined for this tape drive.

Note
If you record a tape using a no-rewind device, you must rewind the tape before you read it.

st is the standard designation for a tape drive.

drive_number is the drive number. It is incremented for each tape drive; if there is only one tape drive attached to the filer or remote host, the number is 0. The assigned drive number persists through reboots.

compression_type is a drive-specific code for the density of data on the tape and the type of compression. The values for compression_type are shown in the following table.

Compression type	Description
`a`	Highest compression
`h`	High compression
`l`	Low compression
`m`	Medium compression

Examples

nrst0a specifies a no-rewind device on tape drive 0 using the highest compression.

remfiler:nrst0a specifies a no-rewind device on tape drive 0 on the remote host remfiler that uses the highest compression.

Caution
When using the urst device with the dump or restore command, ensure that the tape drives it is used with are stackers and that there are sufficient tapes in the stacker sequence. Otherwise, the tape drives involved will terminate the command sequence or overwrite the same tape multiple times.

Sample listing of tape devices

The following example shows the tape devices associated with a Digital^TM DLT7000:

rst0l - rewind device, format is: 81633 bpi 40 GB (w/comp)

nrst0l - no rewind device, format is: 81633 bpi 40 GB (w/comp)

urst0l - unload/reload device, format is: 81633 bpi 40 GB (w/comp)

rst0m - rewind device, format is: 85937 bpi 35 GB

nrst0m - no rewind device, format is: 85937 bpi 35 GB

urst0m - unload/reload device, format is: 85937 bpi 35 GB

rst0h - rewind device, format is: 85937 bpi 50 GB (w/comp)

nrst0h - no rewind device, format is: 85937 bpi 50 GB (w/comp)

urst0h - unload/reload device, format is: 85937 bpi 50 GB (w/comp)

rst0a - rewind device, format is: 85937 bpi 70 GB (w/comp)

nrst0a - no rewind device, format is: 85937 bpi 70 GB (w/comp)

urst0a - unload/reload device, format is: 85937 bpi 70 GB (w/comp)

The abbreviations in the example are defined as follows:

bpi--bits per inch; this is the density of the tape.
GB--gigabytes; this is the capacity of the tape.
w/comp--with compression; this shows the tape capacity with compression.