Hitachi GAD with ALUA Delivers Local HA for SAP HANA

A real-world look at how Hitachi GAD and ALUA-based multipathing solved a single point of failure for SAP HANA Enterprise storage.

Problem Statement

A customer running a business-critical SAP HANA environment experienced a significant outage when one of their storage systems went down unexpectedly. SAP HANA became immediately unavailable, operations were disrupted, and recovery took far longer than the business could tolerate. The root cause was straightforward — no local high availability protection on the storage layer. A single failure was all it took.

This is a rare case because enterprise storage systems are built with dual controllers for redundancy, but when it does happen, the consequences for a business-critical SAP HANA environment can be severe. Many organizations invest heavily in SAP HANA for its performance and reliability yet leave the underlying storage as a single point of failure. When we evaluated the customer's environment, the path forward was clear: implement local High Avalability (HA) using Hitachi Global-Active Device (GAD) with ALUA-optimized multipath I/O.

Solution Overview

GAD is a synchronous storage replication technology available on Hitachi Virtual Storage Platform (VSP) systems. It maintains two fully synchronized, active copies of data across two storage systems — both live and serving I/O simultaneously.

Unlike traditional active-passive replication where the secondary copy sits idle, GAD operates in an active-active model. It provides zero Recovery Point Objective (RPO) and continuous data availability across two sites. For mission-critical SAP HANA environment, GAD offers compelling advantages including controller/array failure protection for local storage HA.

The following figure shows the solution overview as an example using three servers. In the configuration, the Primary and Secondary storage systems connect to the HANA host server(s). If a failure occurs in one storage system, you can use alternate path software to switch server I/O to the Secondary storage.

Why We Chose ALUA Over HDLM

ALUA (Asymmetric Logical Unit Access) is a SCSI standard that enables a host to identify and set the relative preference of different I/O paths to a storage volume. In a GAD configuration, the SAP HANA server has paths to both storage systems simultaneously. With ALUA enabled:

• Optimized paths (to the preferred storage) carry the Primary I/O load
• Non-optimized paths (to the Secondary storage) remain on standby
• On storage failure, the multipath driver automatically promotes standby paths — transparently to SAP HANA

Hitachi has traditionally offered HDLM (Hitachi Dynamic Link Manager) as its proprietary multipath driver for VSP environments. However, it is generally preferred to use Linux native multipathing technologies that are supported by enterprise Linux distributions and widely adopted in SAP-certified storage solutions. This approach avoids the additional support and maintenance complexity associated with third-party proprietary multipathing software.. Refer to SAP note 3359552 (SAP user ID required) for 3^rd party software supportability considerations. Therefore, we validated DM-Multipath with ALUA, rather than vendor-proprietary HDLM to align with SAP's certification requirements and support boundaries.

What We Validated

We conducted an evaluation of GAD with ALUA for SAP HANA in our engineering lab including key SAP HANA functionalities in the table below for different GAD operation states. Our findings showed that SAP HANA remained fully operational during storage failure, and the HANA database did not need to be restarted.

GAD Operation State	HANA System Check	Result
·       GAD Pairs in “PAIR” ·       Split GAD Pairs ·       Shutdown Primary array ·       Fallback to Primary array	Start/Stop HANA System	HANA processes started with “GREEN” and stopped with “GRAY”
	Multipath states	Verify all data paths are active, two preferred optimized paths for Primary storage, two non-preferred paths for Secondary storage
	Run HCMT Consistency Test	Resilience test to verify /hana/data, /hana/log, /hana/shared filesystems are correctly configured, mounted and meet HANA’s requirements
	HANA Scale-out failover HA test	Verifies HANA Scale-out continuous operation without interruption when failover and failback occur for worker node and master node

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GAD does not negatively impact SAP HANA functionality, however it introduces additional latency in the write path due to its synchronous nature and the need for cross-site coordination overhead impact on I/O throughput.

Business Value

For the customer, the move to GAD with ALUA delivered outcomes:

• Near-Zero RTO (Recovery Time Objective)
•  Zero RPO (Recovery Point Objective) – data is replicated synchronously
•  Metro-site DR resilience for SAP HANA Scale-up
• Controller/storage failure protection for local storage HA
• Non-Disruptive Migration and Upgrade – GAD can be used to migrate workloads across storage arrays without downtime, enabling a smooth transition during datacenter moves or hardware refreshes

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