Serial Attached SCSI technologies and architectures, 4th edition

Dual-domain SAS: servers in two-node cluster

In this configuration, also known as a high-availability cluster, at least one server must have access to

the storage network. The cluster interconnect provides redundancy in the event of HBA or cable failure

(Figure 10). Dual-domain SAS requires active/active configurations that permit both controllers to

process IO transfers. Either controller can act as a standby. To use the dual-ports for redundant

pathways, all drives must be SAS drives, not SATA drives.

Figure 10: Multi-path, 2-node, high availability cluster configuration

Dual-path with cascaded JBODs

Dual paths can prevent a single point of failure in complex enterprise configurations such as

cascaded JBODs. Both SAS and SATA drives support dual-path configurations. This configuration

connects a controller to the IO module at each end of a set of cascaded JBODs. Each JBOD contains

a single expander, as shown in Figure 11. This configuration requires half as many IO modules and

expanders as other redundant storage configurations, so it is economical.

JBOD

SAS drive

Server

HBA

Server

HBA

Cluster

interconnect

IO Module

Expander

IO Module

Expander

IO Module

Expander

IO Module

Expander

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