Dell NetWorker 19.9 Administration Guide

To enable NetWorker to use the maximum tape capacity, select the highest density device driver for the device. Additional reasons that the server appears to fill tapes prematurely include:

• Write errors occur during a backup. With any tape error, the NetWorker server marks the tape as full. To prevent tape write errors, clean the tape drive regularly and use only data-quality tapes. If cleaning the drive does not help, ensure that you perform the following actions:
  • Confirm the configuration of the device driver.
  • Set any necessary switch settings on the tape drive, based on the manufacturer specifications.
  • Confirm that all cables are secure.
  • Address other potential SCSI problems.
• Space requirements for NetWorker to create file marks. The NetWorker server periodically writes file marks to facilitate rapid recovery of data. These file marks consume varying amounts of tape space, depending on the type of tape drive. The number of file marks the server writes to the tape depends on how many save sets are on the tape. Many small save sets require more file marks than a few larger ones.
• Tape capacity differences. Two apparently identical tapes from the same vendor can vary significantly in capacity. This can cause problems when you copy one full tape to another, especially if the destination tape holds less data than the source tape.
• Data compression affects the tape capacity. If you use compression on the tape drive, you cannot predict the effect on tape capacity. A compressing drive can provide twice the capacity of a non-compressing drive. Tape capacity can vary depending on the type of backup data. For example, if a non-compressing drive writes 2 GB of data to a specific tape, the compressing drive could write 10 GB, 2 GB, 5 GB, or some other unpredictable amount of data.
• Tape length. Verify the tape lengths, for example, a 120-meter DAT tape holds more data than a 90-meter DAT tape.