ALUA mode of UltraPath

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In the multipath state, the asymmetric logical unit access (ALUA) mode presents active/passive LUNs to the host and provides an access status switching interface to switch the LUNs' working controller.
SCSI (SPC) ALUA:
1. Defines the status model of target ports (front-end ports of storage arrays).
2. Describes the SCSI commands used for querying and managing port status.
The multipath software:
1. Uses SCSI commands to query target port status, obtain the path priority, and manage paths.
2. Employs control commands to access target ports in different states to select the optimal path.
3. Uses SCSI commands to set port status to control the path priority.
In short, ALUA is a SCSI port model and port management mode. It enables host multipath software to manage paths based on the mode.

Other related questions:
Introduction to UltraPath
OceanStor UltraPath (UltraPath for short) is a piece of multipath software developed by Huawei. It works as a driver on an operating system's kernel, controls access from an application server to a storage system, as well as selects and manages paths between them. UltraPath improves the efficiency and reliability of data transfer between an application server and a storage system, serving as a simple, convenient, and efficient storage path management solution.

ALUA policy of the OceanStor V3 storage
On OceanStor V3, the default policy of ALUA is disabled by default. 1. If the storage system is in dual-controller mode and the third-party multipathing software is used, you are advised to enable ALUA. 2. If the storage system has four or more controllers, you must disable ALUA.

Operating systems compatible with UltraPath
Operating systems compatible with UltraPath: FAQ-What operating system is compatible with UltraPath

Method used to configure UltraPath in the cluster environment
You can configure UltraPath in the cluster environment as follows: After you install the UltraPath software in the cluster environment, perform the following configurations: 1. Enable the cluster function. If you are to install UltraPath of the V100R002 version, manually enable the cluster function. If you are to install UltraPath of the V100R003 or V100R005 version, the system automatically enables the cluster function after installing the UltraPath software successfully. Note: The following operations are performed on in the Windows operating system. For details about UltraPath configuration in other operating systems, see the OceanStor UltraPath for XX User Guide. (XX is a specific operating system.) a. On the UltraPath for Windows Manager home page, click the Configuration tab. b. In the Cluster area, select Cluster Enable. c. Click Apply. 2. Set the Persistent Reversed Key (PRKey) of UltraPath to different values. The PRKey value is 00000101 by default. The first six digits from the left 000001 represent a cluster, and the remaining two digits 01 represent a node. Different nodes require different PRKey values. For example, in a dual-node cluster, if the primary node's PRKey value is 00000101 and the secondary node's PRKey value can be 00000102. a. On the UltraPath for Windows Manager main interface, click the Configuration tab. b. In the Persistent Reservation Key area under Cluster, enter different PRKey values. c. Click Apply.

Solution when installing UltraPath fails on CentOS
Solution when installing UltraPath fails on CentOS: This failure occurs because the host is installed with the multipathing software of RDAC, which cannot coexist with Huawei UltraPath. You need to suspend service operations and perform the following steps: 1. Run rpm -e --allmatches UltraPath to uninstall UltraPath completely. 2. Uninstall the multipathing software of RDAC (performed by the customer's maintenance engineer). 3. Restart the host and install UltraPath.

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