Using Native Controller Copy Services

Technote (troubleshooting)


Problem(Abstract)

Native copy services are those provided by a Storage System attached rather than by SVC, Storwize V7000 or Storwize V7000 Unified. This document describes known limitations in their use.

Cause

Source and Target volumes associated with the native copy service may appear/disappear from view or change access state during the copy. This is outside of SVC, Storwize V7000 or Storwize V7000 Unified control and can lead to unexpected behaviour.

Resolving the problem

Use of native copy services is not supported on all storage systems that can be managed by SVC, Storwize V7000 or Storwize V7000 Unified. The following sections give general advice as well as device-specific advice for those storage systems where native copy services are supported.

General Advice

  1. The management interface for the native copy service has no knowledge of SVC, Storwize V7000 or Storwize V7000 Unified. EXTREME CARE must be exercised when selecting Source and Target volumes as inadvertent selection of a volume that is managed by SVC, Storwize V7000 or Storwize V7000 Unified can take the whole storage pool and all associated volumes offline.
  2. Native copy service Source and Target volumes may be exported to SVC, Storwize V7000 or Storwize V7000 Unified, providing:
    • they are left as unmanaged Mdisks, or
    • they are exported from SVC, Storwize V7000 or Storwize V7000 Unified as image mode cache-disabled volumes
  3. During the execution of a native copy service:
    • a Target volume may be created and subsequently discovered by SVC, Storwize V7000 or Storwize V7000 Unified. Unless access to this volume by SVC, Storwize V7000 or Storwize V7000 Unified is required, leave it as an unmanaged Mdisk
    • the Source and Target volumes may change access state (read/write, read-only, none) either permanently or transiently. If these volumes are managed by SVC, Storwize V7000 or Storwize V7000 Unified, expect SVC, Storwize V7000 or Storwize V7000 Unified to log errors and possibly take the Mdisk offline
  4. To recover from an offline Mdisk, issue the following commands:
      svctask detectmdisk

      svctask includemdisk <mdisk id/name>

  5. Systems on which native copy service can be used with SVC, Storwize V7000 or Storwize V7000 Unified are:
    • DS3400
    • DS4000
    • DS5000
    • DS6000
    • DS8000
    • EMC Symmetrix



DS3400/4000/5000 (FAStT) Native Copy Services

FlashCopy

A hidden volume (the Repository) is used for data that is written after the FlashCopy is taken. The size of the Repository is user-defined and it can fill up if the capacity is less than that of the Source volume. When the Repository is full, attempting a write access to the Source volume will fail. A FlashCopy option allows this failure to be associated with either the Source or Target volume. In either case, SVC, Storwize V7000 or Storwize V7000 Unified will take the associated Mdisk offline.

Recommendations:

  1. Define the Repository to be of adequate size. Refer to the appropriate Product documentation for instructions.
  2. Select 'Fail FlashCopy Logical Drive' to associate any Repository full failures with the Source volume.

VolumeCopy

VolumeCopy is not supported under SVC, Storwize V7000 or Storwize V7000 Unified.

MetroMirror

The Target volume in a MetroMirror relationship does not accept read/write requests from Hosts at the local site. An SVC, Storwize V7000 or Storwize V7000 Unified at this site will take the Mdisk offline if access to the Target volume is attempted.

During disaster recovery, a MetroMirror Source and Target volumes undergo a role reversal. Each site that has SVC, Storwize V7000 or Storwize V7000 Unified will need to perform a Discovery (svctask detectmdisk) in order to establish the new Mdisk view.

MetroMirror requires the dedicated use of the A2/B2 controller ports. It also requires Source and Target volumes to be owned by the same controller in the local and remote systems i.e. both owned by A or both owned by B.

Recommendations:

  1. Ensure the A1/B1 controller ports are zoned to SVC, Storwize V7000 or Storwize V7000 Unified
  2. The A2/B2 controller ports must be connected to the SAN, zoned together and removed from the SVC, Storwize V7000 or Storwize V7000 Unified zone prior to starting MetroMirror
  3. Avoid exporting the MetroMirror Target volume to SVC, Storwize V7000 or Storwize V7000 Unified
    • If storage partitioning is enabled, DO NOT map the Target volume to SVC, Storwize V7000 or Storwize V7000 Unified
    • If storage partitioning is not enabled, the Target volume will be exported to SVC, Storwize V7000 or Storwize V7000 Unified but it MUST be left as an unmanaged Mdisk

DS6000/8000 and ESS Native Copy Services

FlashCopy

On setting up the FlashCopy, the user can choose the access mode of the Target volume.

Recommendations:

  1. Set the Target volume access mode to read/write

MetroMirror

On setting up the MetroMirror relationship, the user can select the Target volume access mode as either disallowed or read-only for Hosts at the local site. Regardless of this setting, during a full copy, the Target behaves as if the access mode had been set to disallowed.

SVC, Storwize V7000 and Storwize V7000 Unified will take the Target offline if the access mode is disallowed and any access is attempted. It will take the Target offline if the mode is read-only and write access is attempted.

SVC, Storwize V7000 and Storwize V7000 Unified will not discover a Target volume with an access mode of disallowed. An unmanaged Mdisk that changes access mode to disallowed will be removed from the Mdisk view when the next user-initiated Discovery (svctask detectmdisk) is performed.

During disaster recovery, a MetroMirror Source and Target volumes undergo a role reversal. Each site that has SVC, Storwize V7000 or Storwize V7000 Unified will need to perform a Discovery (svctask detectmdisk; svctask includemdisk <mdisk#>) in order to establish the new Mdisk view.

EMC Symmetrix Native Copy Services

The information discussed in the 'General Advice' section is sufficient for dealing with Symmetrix native copy services.


Please refer to the What's new in the IBM System Storage SAN Volume Controller Information Center for more information on SVC Terminology changes.

Cross reference information
Segment Product Component Platform Version Edition
Storage Virtualization SAN Volume Controller 6.4 SAN Volume Controller 4.3, 5.1, 6.1, 6.2, 6.3, 6.4
Disk Storage Systems IBM Storwize V7000 (2076) 6.4 IBM Storwize V7000 6.1, 6.2, 6.3, 6.4
Disk Storage Systems IBM Storwize V7000 Unified (2073) 1.3 Platform Independent 1.3

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Document information


More support for:

IBM Storwize V7000 (2076)
6.4

Version:

Version Independent

Operating system(s):

Platform Independent

Reference #:

S1002852

Modified date:

2008-03-28

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