Data Formatting; Figure 2-7: The Slr140, Slr100, Slr75, Slr60 And Slr7 Buffer System - Tandberg Data SLR7-140 PROGRAMMER Manual

Data Buffer
C om pr es s i on
SC SI Bus
Figure 2-7: The SLR140, SLR100, SLR75, SLR60 and SLR7 Buffer System (Write
Tandberg Data
2.7.1.2. SLR7, SLR60, SLR75, SLR100 and SLR140 Drives
The data buffer in the SLR7, SLR60, SLR75, SLR100 and
SLR140 Drives consists of a single logical unit with a
size of nearly 8 MByte.
The data buffer is used to buffer data from logical
blocks transferred at high-speed (up to 40 MBytes/s)
to/from the SCSI interface. When moved into the buffer
the data is first compressed and then formatted into
frames of physical blocks. The data in the data buffer
is then transferred to/from the media at speeds varying
from up to 6
(SLR7).
D at a
For m at t er
D at a
Logi cal t o Phys i cal M appi ng
Note that the use of the buffer is optimized so that as
long as most logical blocks are of the same size the
complete allocated size for the host buffer is utilized
to buffer data. When mixing blocks of different sizes or
when a very large
through the buffer system, the effective buffer size may
be somewhat less than the physical size.
2.7.2.

Data Formatting

When data are moved from the host buffer to the tape
buffer it is grouped into physical blocks. The physical
blocks are again grouped into frames. In addition to
host related data and tapemarks the frames hold addi-
tional information like error correction codes (ECC) [9]
- [17].
The size of the physical block as well as the number of
blocks per frame depend on the tape format used [9] –
[17].
The tape buffer is used to buffer complete frames. The
maximum number of frames depends on the tape format in
use. With an SLR32 medium for example, the tape buffer
is able to hold up to 16 frames each holding a maximum
2-21 Tandberg SLR Product Line SCSI Functional Specifications
MBytes/s (SLR140)
Logi cal Bl ock
Logi cal Bl ock
Mode)
number of
About Tape Streamers
down to 3 Mbytes/s
D at a Buf f er
Phys i cal Fr am e
Phys i cal Fr am e
Phys i cal Fr am e
M edi um
tapemarks are flowing