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SnapMirror active sync support for AIX: behavior by ONTAP release and migration guidance

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Applies to

  • ONTAP
  • SnapMirror active sync
  • AIX/"PowerVM Virtual I/O Server" (VIOS)
  • SAN environments
  • PowerHA SystemMirror environments

Description

  • SnapMirror active sync (SM-as) is supported with AIX beginning with ONTAP 9.11.1
  • Support behavior differs by ONTAP release:
    • ONTAP 9.11.1 to 9.18.1: Active/Standby support for AIX
    • ONTAP 9.19.1: Active/Active support for AIX for non-disruptive SM-as operation

This article explains support behavior, host impact, and deployment guidance for new and existing AIX environments.

Overview

SnapMirror active sync (SM-as) enables synchronized data copies across two sites for business continuity and disaster recovery. For AIX hosts, operational support and behavior depend on the ONTAP release and the LUN access mode (global or local).

General Support Statement
  • ONTAP 9.11.1 to 9.18.1: AIX is supported in Active/Standby mode. Site failover (planned or unplanned) is disruptive.
  • ONTAP 9.19.1: AIX supports Active/Active non-disruptive operation, requiring access-mode local for LUNs.

Note: AIX support with SM-as is PVR only

SM-as Behavior in ONTAP 9.11.1 through 9.18.1
  • Supported mode: Active/Standby
  • Operational behavior:
    • Primary site handles all active I/O.
    • Secondary site remains on standby.
    • AutomatedFailover (AF) or AutomatedFailoverDuplex (AFD) SnapMirror policies are supported.
    • The Logical Unit (LU) at the secondary site is hidden from the host during normal operation and activated only during disaster or failover.
    • Host rescan and application restart are required for I/O recovery after failover.
  • Technical context: NetApp SCSI LUN uses a single task set across paths and nodes.
  • AIX host impact: Site failover is disruptive; host-side rediscovery and rescan are required before I/O resumes.
  • Customer impact: Plan for disruptive failover behavior in this release range.

For more information refer KB article How to configure AIX Host for SnapMirror active sync in ONTAP 

    SM-as Behavior Starting with ONTAP 9.19.1
    • Supported mode: Active/Active (non-disruptive for AIX)
    • Operational behavior:
      • Both primary and secondary site paths are visible to the host.
      • Recommended to use AutomatedFailoverDuplex (AFD) policy.
      • Secondary site LU is no longer hidden from the host.
      • No host rescan is required after planned or unplanned site failover.
      • AIX SANboot is supported. For a Virtualized environment, especially with boot device on vSCSI devices, it is recommended to modify the rw_timeout value of disk from default 30s to 120s.
    • Policy and design guidance:
      • Use AutomatedFailoverDuplex (AFD) policy.
      • Leverage host proximity settings on igroups for preferred site selection.
    • Technical context: Requires an additional attribute for LUN creation: access-mode local.
    Access Mode for AIX LUNs (ONTAP 9.19.1 and Later)
    • ONTAP 9.19.1 introduces an access-mode attribute for AIX LUN creation.
    • Values:
      • global (default)
      • local (required for Active/Active)
    • It is mandatory to set access-mode local for non-disruptive Active/Active support.

    Example command:

    lun create -vserver -volume -lun -size -ostype aix -access-mode local

    Recommendations
    • For protected LUNs in ONTAP 9.19.1 and later using SM-as Active/Active, always use access-mode local.
    • For unprotected LUNs, access-mode global may be used as needed.
    New Deployment Recommendation
    • Deploy new environments with ONTAP 9.19.1 or later for Active/Active protection.
    • Set access-mode local during LUN creation.
    Existing Deployment Migration to ONTAP 9.19.1 and Above

    Existing AIX environments can be migrated from Active/Standby SM-as to Active/Active using ONTAP 9.19.1 or later. This process requires a planned disruption and careful coordination between host and storage teams.

      • Important limitation: AIX does not dynamically recognize a change from access-mode global to local. The host must close and reopen the device to recognize access-mode local capability.
      • Migration requires a planned disruption window, coordinated host and storage steps, and device rediscovery on AIX.

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