Tandberg Data Streamer SLR140 XE Kit Internal Grey 6721 6934 00 사용자 설명서
제품 코드
6721 6934 00
SLR140 Features
D:\SLR140 Features for Reliability and
Performance.doc
Performance.doc
Page 10 of 13
Printed: 30.03.04
15:17
Large 8 MB Buffer
The SLR7-140 features an 8-MB buffer. With a burst transfer rate of 40 megabytes per sec. data feed
to the tape drive from the host, an empty buffer fills up in 0.2 sec. With a sustained transfer rate of 5
megabyte per sec., the buffer is emptied (data written to the tape) in 1.6 sec. This means that the host
and other devices on the SCSI bus can perform other operations in 1.4 sec. while the tape drive is busy
writing data.
to the tape drive from the host, an empty buffer fills up in 0.2 sec. With a sustained transfer rate of 5
megabyte per sec., the buffer is emptied (data written to the tape) in 1.6 sec. This means that the host
and other devices on the SCSI bus can perform other operations in 1.4 sec. while the tape drive is busy
writing data.
A large 8 MB buffer to store only compressed data before written to the tape media
gives higher sustained transfer rate - optimized to the host’s bus speed
gives higher sustained transfer rate - optimized to the host’s bus speed
SLR140 "Auto-sense" Transfer Rate
With very low transfer rate from the host, and the buffer is not filling up again after the 1.6 sec, the
tape speed is automatically adjusted to accommodate lower speed. The tape speed for SLR140 at 6
MBs is 86 ips (inch per sec.), while the tape speed for 5 MBs is 70 ips. SLR60, SLR75 and SLR100
also have similar functionality.
tape speed is automatically adjusted to accommodate lower speed. The tape speed for SLR140 at 6
MBs is 86 ips (inch per sec.), while the tape speed for 5 MBs is 70 ips. SLR60, SLR75 and SLR100
also have similar functionality.
This feature allows the SLR60/75/100/140 to adjust to the optimum speed on the data transfer from the
host computer and to avoid under-run, and thus allow for maximum performance. Under-run means
that the tape is stopped, and rewind to where the last block of data was written. The tape will start
moving forward when the buffer receives data, and the write operation is continued. This normally
slows down the write operation. Another method used by other technologies to avoid under-run is to
keep the tape media running, and keep on writing “filler”, dummy, or the last block – also called forced
streaming. This method however reduces the total capacity on the media.
host computer and to avoid under-run, and thus allow for maximum performance. Under-run means
that the tape is stopped, and rewind to where the last block of data was written. The tape will start
moving forward when the buffer receives data, and the write operation is continued. This normally
slows down the write operation. Another method used by other technologies to avoid under-run is to
keep the tape media running, and keep on writing “filler”, dummy, or the last block – also called forced
streaming. This method however reduces the total capacity on the media.
SLR optimizes to the host’s bus speed, which gives higher transfer rates and
maximum performance.
maximum performance.
Ultra2 SE/LVD Interface
Most hard disks now in the market are using the Ultra160 or Ultra320 interface, which allows a burst
transfer rate up to 160 and 320 megabytes per sec. (MBs). Also for the SCSI interface, backward
compatibility is important, and embedded. The Ultra160 protocol allows devices with older interfaces
to be connected to the same bus. Ultra2 devices can be connected to an Ultra160 interface bus, and an
Ultra2 bus supports the older Wide Ultra and Ultra with only 20MBs transfer rate.
transfer rate up to 160 and 320 megabytes per sec. (MBs). Also for the SCSI interface, backward
compatibility is important, and embedded. The Ultra160 protocol allows devices with older interfaces
to be connected to the same bus. Ultra2 devices can be connected to an Ultra160 interface bus, and an
Ultra2 bus supports the older Wide Ultra and Ultra with only 20MBs transfer rate.
The Ultra2, and newer SCSI interfaces also utilizes the Low Voltage Differential (LVD) Signaling
feature. LVD allows up to 12 meter of cable between the host interface adapter and the last device,
whilst the Single Ended (SE) interface used for older SCSI protocols only allows 1.5 meter of cable.
Using an interface that allows a long cable becomes more and more important as rack mounting is
more and more used. The host computer or server can then be installed in one rack, while other
devices like a tape drive or an automation product can be connected on the same bus in another rack
several meters away.
feature. LVD allows up to 12 meter of cable between the host interface adapter and the last device,
whilst the Single Ended (SE) interface used for older SCSI protocols only allows 1.5 meter of cable.
Using an interface that allows a long cable becomes more and more important as rack mounting is
more and more used. The host computer or server can then be installed in one rack, while other
devices like a tape drive or an automation product can be connected on the same bus in another rack
several meters away.
The SCSI backwards compatibility has some limitations – e.g. if an Ultra or Wide Ultra device which
only allows the SE interface - is connected to a Ultra2 bus, the whole bus is limited to the slowest SCSI
protocol, and shortest cable length. If this device is connected to the same bus as hard disk drives or
other devices, the Ultra/Wide Ultra device will slow down the performance of the whole system. Also
the flexibility of installation will be limited of the shorter cable.
only allows the SE interface - is connected to a Ultra2 bus, the whole bus is limited to the slowest SCSI
protocol, and shortest cable length. If this device is connected to the same bus as hard disk drives or
other devices, the Ultra/Wide Ultra device will slow down the performance of the whole system. Also
the flexibility of installation will be limited of the shorter cable.