Pair condition and recovery: path failure, primary to secondary storage system

Global Active Device for VSP One Block
Version
10.5.x
File Size
25537 KB
Audience
anonymous
Part Number
MK-23VSP1B011-11
ft:lastEdition
2026-06-23

If the statuses of storage systems in both the primary and secondary sites are normal, a failure might have occurred in a physical path or switch between the storage systems. You can correct the issue by recovering the paths and resynchronizing the pair.

GAD pairs might be created between the primary and secondary sites that configure GAD as follows:

  • A P-VOL of a GAD pair is at site 1 and a S-VOL is at site 2.
  • A P-VOL of a different GAD pair is at site 2 and a S-VOL is at site 1.

In this case, recover from a physical path failure at the secondary site. For more information, see Pair condition and recovery: path failure, secondary to primary storage system.

The following table shows transitions for pair status and I/O mode, the volumes that are accessible from the server, and the location of the latest data when you can no longer use any physical path from the primary storage system to the secondary storage system.

Before failure

After failure

Pair status and I/O mode

Pair status and I/O mode

Volume accessible from the server

Volume with latest data

P-VOL

S-VOL

P-VOL

S-VOL

P-VOL

S-VOL

PAIR (Mirror(RL))1

PAIR (Mirror(RL))1

PSUE (Local)

PSUE (Block)

OK

NG

P-VOL

PAIR (Mirror(RL))

PAIR (Block)

PSUE (Local)

PAIR (Block)

OK

NG

P-VOL

COPY (Mirror(RL))

COPY (Block)

PSUE (Local)

PSUE/COPY (Block)2

OK

NG

P-VOL

PSUS/PSUE (Local)

SSUS/PSUE (Block)

PSUS/PSUE (Local)

SSUS/PSUE (Block)

OK

NG

P-VOL

PSUS/PSUE (Block)

SSWS (Local)

PSUS/PSUE (Block)

SSWS (Local)

NG

OK

S-VOL

Notes:

  1. The I/O modes for the P-VOL and S-VOL can change, even if I/Os are not issued from the server to the P-VOL. For example, a command that synchronizes the storage system at the primary site and the storage system at the secondary site might be issued to the P-VOL due to its health check (such as by ATS). When you execute this command, synchronization fails if a path between these storage systems has a failure. As a result, the I/O mode for the P-VOL to which I/Os were not issued from the server becomes Local, and the I/O mode for the S-VOL to which I/Os were issued becomes Block. This might cause a failure and suspend GAD pairs.
  2. If either of the following conditions is met, the S-VOL might become COPY (Block):
    • No volume is set for the quorum disk.
    • A quorum disk failure occurs.

SIMs

  • Primary storage system: DD0xyy, 2180xx
  • Secondary storage system: DD3xyy
  1. Recover the paths from the primary storage system to the secondary storage system.
  2. Resynchronize the pair.
    If a failure occurs after the one volume capacity of a GAD pair can be expanded, the creation, resync, swap resync, and horctakeover operations of the GAD pair cannot be performed because the capacity of both the volumes is not the same. Make sure to expand the other volume capacity so that the capacity of both the volumes is the same, and then retry the operation.