Quantum Audio DAT72 Manuale Utente

Installing internal tape drives

Reviewing Drive Default Settings

Data Compression

The internal tape drive provides two switches for controlling data compression.

Switch 1 determines whether hardware data compression is enabled or disabled. By default, switch 
1 is set to ON, enabling hardware data compression. To disable hardware data compression, set 
switch 1 to the OFF position.

Switch 2 controls whether SCSI commands are recognized for enabling or disabling hardware data 
compression. By default, switch 2 is set to ON, allowing SCSI commands to be used to enable or 
disable hardware data compression. To prevent SCSI commands from enabling or disabling hard-
ware data compression, set switch 2 to the OFF position.

When data compression is enabled, the drive compresses all data written to tape and decompresses 
all compressed data read from tape. The degree of compression varies due to the type of data being 
processed.

Data with a high degree of redundancy, such as structured database files or graphics files, 
are compressed most efficiently, often at a ratio of 2:1 or more.

Data with little redundancy, such as executable programs, are compressed the least.

Media Recognition System (DDS-4 Drives Only)

Using non-DDS media may appear to give satisfactory results, but the inferior specifications of such 
media can cause data-integrity problems. To avoid these problems, the internal tape drive provides 
a media-recognition system (MRS) feature that determines whether tape cartridges conform to the 
DDS tape standard.

By default, switch 3 is set to ON, enabling MRS. With this setting, the drive:

Reads from and writes to MRS media.

Reads from but does not write to non-MRS media.

To disable MRS, set switch 3 to the OFF position. With this setting, the drive reads from and writes to 
MRS and non-MRS media.