Cabling Your System for Joined-Bus, Split-Bus, or Cluster Mode
How you cable your storage system to your host system(s) depends on the bus configuration you choose: joined-bus, split-bus, or cluster.
- A joined-bus configuration is one in which two SCSI buses are joined to form one contiguous bus.
- A split-bus configuration enables you to connect your storage system to either one server with a multichannel RAID controller, or to two servers. However, if one server fails, information controlled by that server is inaccessible.
- A cluster configuration offers multiple paths to the system, which provides high data availability.
Joined-Bus Configuration
Split-Bus Configuration (One Server)
Cluster Configuration or Split-Bus Configuration (Two Servers)
SCSI ID Assignments
| Configuration |
Cables
Used |
SCSI IDs Used |
| 15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Joined-bus |
1 |
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H |
S |
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| Split-bus—primary EMM |
1 |
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H |
S |
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| Split-bus—secondary EMM |
1 |
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H |
S |
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| Cluster |
2 |
S |
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H |
H |
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NOTE: The unshaded SCSI IDs are available for hard-drive use as indicated for each configuration. The reserved SCSI IDs are used as follows:
H = used by the host system initiator.
S = used by the storage system SES. |
SCSI ID Numbers and Associated Hard Drives
Split-Bus Module Modes
| Mode |
LED Icon |
Position of Bus Configuration Switch |
Function |
| Joined-bus mode |
|
Top |
LVD termination on the split-bus module is disabled, electrically joining the two SCSI buses to form one contiguous bus. In this mode, neither the split-bus nor the cluster LED indicators on the front of the system are illuminated. |
| Split-bus mode |
|
Center |
LVD termination on the split-bus module is enabled and the two buses are electrically isolated, resulting in two seven-drive SCSI buses. The split-bus LED indicator on the front of the system is illuminated while the system is in split-bus mode. |
| Cluster mode |
|
Bottom |
LVD termination is disabled and the buses are electrically joined. The cluster LED on the front of the system is illuminated while the system is in cluster mode. |
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