Physical characteristics of the scsi interface, Using multiple scsi buses, Maximum – Dell TL2000 User Manual
Page 47: Length, Between, Terminators, Recommended, Quantity, Drives, Scsi
Note:
For
maximum
performance,
it
is
recommended
to
have
a
maximum
of
one
drive
per
SCSI
bus.
–
Only
use
the
maximum
system-to-device
cable
length
of
25
m
(82
ft)
when
attaching
directly
to
one
device
(a
point
to
point
interconnection).
Physical
Characteristics
of
the
SCSI
Interface
The
library
operates
as
a
set
of
SCSI-3
devices.
The
Ultrium
Tape
Drives
attach
to
servers
using
an
LVD
Ultra160
SCSI
interface.
Each
SCSI
drive
sled
uses
shielded,
HD68-pin
connectors,
and
can
attach
directly
to
a
2-byte-wide
SCSI
cable.
Any
combination
of
up
to
two
initiators
(servers)
and
up
to
four
targets
(devices)
is
allowed
on
a
single
SCSI
bus
if
the
following
conditions
are
met:
v
The
SCSI
bus
is
terminated
properly
at
each
end
v
Cable
restrictions
are
followed
according
to
the
SCSI-3
specification
Under
the
SCSI-3
protocol,
this
type
of
attachment
allows
cable
lengths
of
up
to
25
m
(81
ft)
with
the
appropriate
cable
and
terminator.
The
table
below
gives
the
maximum
bus
length
between
terminators
for
the
LVD
interface.
Table
3-2.
Maximum
bus
length
between
terminators
Type
of
Interconnection
Maximum
Bus
Length
Between
Terminators
(in
meters)
Point-to-point
(1
server
and
1
drive)
25
Multi-drop/daisy-chain
(1
server
and
multiple
drives)
12
(LVD)
Note:
The
maximum
bus
lengths
stated
in
this
table
include
the
internal
length
of
the
bus.
For
maximum
performance,
multiple
SCSI
buses
may
be
required
(see
and
Ultrium
Tape
Drives
must
be
the
only
target
devices
that
are
active
on
the
bus.
Note:
For
maximum
performance,
the
quantity
of
tape
drives
that
you
can
attach
to
one
SCSI
bus
is
limited,
and
is
based
on
the
type
of
bus
that
you
have
and
the
amount
of
data
compression
achieved.
Ultra160
SCSI
buses
have
a
bandwidth
of
160
MB
per
second.
The
table
below
lists
the
types
of
SCSI
buses
and
gives
the
recommended
maximum
quantity
of
drives
that
you
can
attach.
Table
3-3.
Recommended
maximum
quantity
of
drives
per
SCSI
bus
Type
of
Drive
Ultra
160
SCSI
Bus
LVD
Ultrium
3
1
drive
at
2:1
compression
Using
Multiple
SCSI
Buses
The
library
has
two
SCSI
connectors
for
each
tape
drive
in
the
library.
Each
drive
can
be
daisy-chained
using
a
SCSI
bus
jumper.
Removal
of
any
jumpers
will
create
a
SCSI
bus
for
each
drive
installed
in
your
library
for
attachment
to
multiple
servers
or
to
multiple
SCSI
adapter
cards
on
one
server.
Remember
that
each
SCSI
bus
must
be
terminated.
Multiple
SCSI
buses
may
be
required
for
maximum
performance,
depending
on
the
application
and
data
compression
ratio.
Note,
however,
that
library
(Medium
Changer)
control
is
required
on
at
least
one
SCSI
bus.
Chapter
3.
Installation
Planning
3-7