HP Visualize J5000 hp Visualize J5000, J7000 workstations owner's guide (a4476 - Page 94

Device Files - Data Compression If you wish to use the data compression feature, use the device files /dev/rmt/3hc and /dev/rmt/3hcn, which are set for SCSI ID 3. If you use the /dev/rmt/3hc device file, the tape drive compresses the data and rewinds the data cassette every time the system releases the drive from its control. If you use the /dev/rmt/3hcn device file, the drive compresses the data, but does not rewind the data cassette. The tape stays where it was after the last operation. If you use these device files, you do not need to create any device files. The tar (tape file archiver) command saves files to a data cassette, restores files from a data cassette, or lists files on a data cassette. Archiving Data in Compressed and Noncompressed Mode This section describes how to transfer data to and from a DDS- format data cassette (saving and restoring) using the HP-UX tar command and your tape drive's device file. NOTICE: Before using your DDS-format tape drive to back up your file system, make sure you read the "Media Interchangeability Restrictions" section later in this chapter. The tar (tape file archiver) command allows you to save files to a data cassette, restore files from a data cassette to your system, or list files on your data cassette. The examples in this chapter use the device file /dev/rmt/3m, which archives the data in noncompressed mode and causes the drive to rewind the data cassette. To use data compression, substitute /dev/rmt/3hc for /dev/rmt/3m. If you named your device files differently, substitute the correct file name where appropriate. 4-13