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DuraStor 7220SS storage subsystem's without the cost of external
hardware, other than cables.
Host 1
Host Link 1
FC HBA
Host 2
FC HBA
Host Link 2
Figure 3-48 Active-Active Single-Port Hubs Enabled
SAN Configuration Not Supported
In the active-active dual-port configuration with two independent
hubs or the internal hub, two single-ported hosts are not
supported. The issue with this configuration is that if a controller
fails, each host loses access to one of the LUNs. For example, if
Controller 1 fails, Host 1 can no longer access LUN 2, because Port
2 on Controller 2 has changed from presenting its own LUNs to
presenting Controller 1's LUNs. A need for this SAN configuration
can arise if multiple single-ported hosts need access to LUNs from
both controllers, and two hubs are desired to improve performance
by decreasing loop access contention.
Note that this SAN is only partially fault-tolerant because the hubs
and controllers have redundant hardware, but the hosts do not.
The problem with this configuration can be overcome by using a
single switch at the cost of replacing the two hubs with a switch. If
loop access contention is not an issue, then the single hub
configuration works as well.
DuraStor FC RAID Appliance
FC2
FC1
HUB
P2
HUB
P1
FC1
P3
FC2
P4
Installing the DuraStor Storage Subsystem
CH0
LUN 2
Passive
CH1
LUN 2
CH2
Active
CH3
Controller 2
LUN 1
CH0
Active
T
CH1
T
LUN 1
CH2
Passive
T
CH3
Controller 1
T
CH0
Up to 12 Disk Drives
CH1
Up to 12 Disk Drives
CH2
Up to 12 Disk Drives
CH3
Up to 12 Disk Drives
3-53
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