3-53
Installing the DuraStor Storage Subsystem
DuraStor 7220SS storage subsystem’s without the cost of external
hardware, other than cables.
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.
Host 2
FC HBA
Host 1
FC HBA
Host Link 1
Host Link 2
Up to 12 Disk Drives
Up to 12 Disk Drives
Up to 12 Disk Drives
Up to 12 Disk Drives
FC2
FC1
FC1
FC2
Controller 2
Controller 1
LUN 2
Active
LUN 2
Passive
LUN 1
Active
LUN 1
Passive
P2
DuraStor FC RAID Appliance
CH0
CH0
CH1
CH1
CH2
CH2
CH3
CH3
CH0
CH1
CH2
CH3
P1
P3
P4
HUB
HUB
T
T
T
T
DuraStor IUG.book Page 53 Wednesday, January 30, 2002 10:49 AM