Tandberg Data Streamer SLR140 Internal Grey 6720 6784 00 Benutzerhandbuch
Produktcode
6720 6784 00
SLR140 Features
D:\SLR140 Features for Reliability and
Performance.doc
Performance.doc
Page 4 of 13
Printed: 30.03.04
15:17
The newer SCSI interfaces – Ultra160 and Ultra320 supports the older Ultra2 interface. This means
that an Ultra 2 device can run at its maximum speed without slowing down any Ultra160 or Ultra320
device.
that an Ultra 2 device can run at its maximum speed without slowing down any Ultra160 or Ultra320
device.
Data transmitted from remote server – speed limited to the speed of the line vs. directly attached to the
server – speed limited to maximum sustained transfer rate of the tape drive.
Data compression
Some types of data can not be compressed e.g. pictures and Zip files, and others can be compressed
more than ten times e.g. text, numbers. In an office environment there is a mix of these types of data.
Dependant on type of company, and what kind of data the company normally uses, an average
compression ratio can be much more than 2:1 as the tape drive industry normally is using as a
guideline. This means that a tape drive with hardware data compression should ideally be able to
increase the transfer rate with the same factor as the data is compressed. If then data is compressed two
times, the actual sustained transfer rate should double, and if data is compressed six times, the actual
sustained transfer rate, and capacity should be six times the native transfer rate.
more than ten times e.g. text, numbers. In an office environment there is a mix of these types of data.
Dependant on type of company, and what kind of data the company normally uses, an average
compression ratio can be much more than 2:1 as the tape drive industry normally is using as a
guideline. This means that a tape drive with hardware data compression should ideally be able to
increase the transfer rate with the same factor as the data is compressed. If then data is compressed two
times, the actual sustained transfer rate should double, and if data is compressed six times, the actual
sustained transfer rate, and capacity should be six times the native transfer rate.
There are several compression algorithms on the market. The most known is Zip – a software data
compression. Another very effective compression algorithm used by several tape drive technologies,
including SLR, is ALDC. Average compression ratio by ALDC is somewhat higher than 2:1. Some
tape drive manufacturers are thus using 2.6:1 compression ratio. However all hardware using the
ALDC data compression algorithm will experience the same data compression of a certain set of data.
– up to a maximum compression limited by the factors explained below.
compression. Another very effective compression algorithm used by several tape drive technologies,
including SLR, is ALDC. Average compression ratio by ALDC is somewhat higher than 2:1. Some
tape drive manufacturers are thus using 2.6:1 compression ratio. However all hardware using the
ALDC data compression algorithm will experience the same data compression of a certain set of data.
– up to a maximum compression limited by the factors explained below.
The actual speed of the backup is however limited not only to how many times the data can be
compressed and how fast a tape drive can write data on the tape media, but also how fast the
electronics and firmware inside the tape drive can process the data before the data is written to the tape.
A slow electronics or firmware process inside the tape drive will limit the actual transfer rate to a
certain maximum speed even if the data is compressed several times.
compressed and how fast a tape drive can write data on the tape media, but also how fast the
electronics and firmware inside the tape drive can process the data before the data is written to the tape.
A slow electronics or firmware process inside the tape drive will limit the actual transfer rate to a
certain maximum speed even if the data is compressed several times.
Data on the hard disk is normally not compressed – except for Zip files. This means that data
transferred from the hard disk to a tape drive with hardware data-compression, are “shrunk” by a factor
of X before written to the tape media. When transferred from the tape media to the hard disk, the data
is “un-shrunk” to the full size again before written to the hard disk. Again, the shrinkage – or
compression ratio depends on the type of data and somewhat on the compression algorithm.
transferred from the hard disk to a tape drive with hardware data-compression, are “shrunk” by a factor
of X before written to the tape media. When transferred from the tape media to the hard disk, the data
is “un-shrunk” to the full size again before written to the hard disk. Again, the shrinkage – or
compression ratio depends on the type of data and somewhat on the compression algorithm.
MLR
MLR
Hard
disk
disk
Tape
drive
drive
100 megabit line
Max. speed:
4 - 5 megabyte/sec
4 - 5 megabyte/sec
Hard
disk
disk
Wide Ultra2
Max. speed:
80 megabyte/sec
80 megabyte/sec