Dell POWERVAULT MD3600I - Manual (Page 181)

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Configuring Asymmetric Logical Unit Access
If your MD Series RAID storage array supports Asymmetric Logical Unit Access (ALUA), active-active throughput allows
I/O to pass from a RAID controller module to a virtual disk that is not owned by the controller. Without ALUA, the host
multipath driver is required to send data requests targeted to a specific virtual disk to the owning RAID controller
module. If the controller module does not own the virtual disk, it rejects the request.
ALUA Performance Considerations
While ALUA enables an MD-series storage array with a dual-controller (duplex) configuration to service I/O requests
through either RAID controller module, performance is decreased when the non-owning RAID controller module
accesses a virtual disk. To maintain the best possible throughput, the host driver communicates with the controller
firmware to send data requests to the owning RAID controller, if possible.
Automatic Transfer Of Ownership
The RAID controller firmware automatically transfers virtual disk ownership if more than 75 percent of data I/O over the
previous five minutes was routed to the non-owning RAID controller. This indicates that either the storage array has lost
redundant connections or that some of the data paths to the virtual disk or disk group are not usable. MD Storage
Manager launches the Recovery Guru (Virtual Disk Not on Preferred Path) if the condition still exists after the default
alert five-minute delay time has expired. For more information, see
Recovery Guru .
Native ALUA Support On Microsoft Windows And Linux
The following operating systems supported by your MD Series storage arrays also support ALUA natively:
• all supported Microsoft Windows operating systems
• Red Hat Enterprise Linux 6.2
• SUSE Linux Enterprise Server 11.2 with Service Pack 2
NOTE: No configuration steps are required to enable ALUA on the operating systems listed above.
Enabling ALUA On VMware ESX/ESXi
VMware ESX version 4.1 (update 1 and update 2) and ESX/ESXi 5.0 do not have Storage Array Type Plug-in (SATP) claim
rules automatically set to support ALUA on the MD Series storage arrays. To enable ALUA, you must manually add the
claim rule.
Manually Adding SATP Rule In ESX 4.1 (Update 1 And Update 2)
To manually add the SATP rule in ESX 4.1 (update 1 and update 2):
1. Run the following commands to delete the old claim rule and set the Dell-required rule:
– # esxcli nmp satp deleterule –s VMW_SATP_LSI –V DELL –M array_PID
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