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Configurations with ShadowImage

Universal Replicator (UR) and ShadowImage (SI) can share the same data volumes to provide multiple copies of data at both the primary and secondary sites.

Overview of UR/SI configurations

The main function of Universal Replicator is to provide copies of production volumes in a remote location.

Using SI to back up the UR volumes or using UR to back up the SI volumes provides additional advantages.

  • When the UR primary volume is shared with SI:
    • On-site data backup is provided in case of a UR failure.
    • Multiple copies of production data are provided at the primary site for secondary purposes such as data analysis and testing.
  • Sharing the SI secondary volume with the UR primary volume at the primary site provides a remote copy.
  • When SI is cascaded at the secondary site, data in the SI secondary volume can be used for testing the UR system and for recovery purposes.
    • The SI secondary volume is available for continuous replication during a test.
    • If a UR problem is encountered during an actual recovery procedure, the SI secondary volume provides a golden copy of the UR secondary volume, which can be used to restore the UR secondary volume.
Note
  • To split the SI pairs in a consistency group whose volumes are also used in UR pairs, the UR pairs must be in PAIR, PSUS, or PSUE status.

  • (VSP Gx00 models and VSP Fx00 models, VSP E series) An SI pair volume can be used with UR volumes if extended.

The following shared UR/SI configurations are described in this appendix:

Configurations with SI primary volumes

An SI P-VOL can be shared with a UR P-VOL or S-VOL.

  • An SI P-VOL shared with the UR P-VOL is illustrated below. This configuration allows you to use SI for on-site data backup in case of a UR failure, and to use UR to provide a secondary backup of the SI P-VOL in case of an SI failure.GUID-1D942CD4-9253-4C15-8B06-CB4E213EFE2C-low.png
  • A UR S-VOL shared with an SI P-VOL is illustrated below. With this configuration, multiple backup copies of the UR P-VOL can be made on the secondary storage system.
    CautionWhen you share a UR S-VOL with an SI P-VOL as shown in the following figure, the restore operation to the UR S-VOL takes time. This is especially the case when the SI pair is in the PSUS(SP)/PSUS status because of the time needed to copy the SI pair.

    Because of the extra time that might be needed, make sure the UR journal volume is sized with enough capacity to handle the possible increase in I/O. If journal volume capacity is insufficient, the pair will be suspended because of failure.

    GUID-53FB6144-7F47-49DE-B9C1-EA1CA3711B14-low.gif
  • UR primary and secondary volumes shared with SI primary volumes is illustrated below. This configuration provides multiple copies of the source volume at the primary and secondary sites. GUID-F360160A-467C-47D6-8FDA-8DA429ACEB19-low.png

    In the above configurations in which the SI P-VOL is shared, you can only delete UR pairs when the SI P-VOL status is COPY(RS-R)/RCPY. The following table shows possibilities of UR pair operations according to the SI P-VOL status.

    UR pair operations

    SI P-VOL status

    (VSP 5000 series) COPY(PD)/COPY

    COPY(SP)/COPY

    COPY(RS)/COPY

    (VSP G/F350, G/F370, G/F700, G/F900, VSP E series)

    COPY

    PAIR

    (VSP 5000 series) PSUS(SP)/PSUS

    (VSP G/F350, G/F370, G/F700,G/F900, VSP E series)

    PSUS(SP)

    PSUS

    PSUE

    (VSP 5000 series)

    COPY(RS-R)/RCPY

    (VSP G/F350, G/F370, G/F700, G/F900, VSP E series)

    RCPY

    CreateYes*Yes*Yes*Yes*No
    Split P-VOL specifiedYesYesYesYesNo
    Split S-VOL specifiedYesYesYesYesNo
    Resync P-VOL specifiedYesYesYesYesNo
    Resync S-VOL specifiedYesYesYesYesNo
    DeleteYesYesYesYesYes
    Switch operations between the primary and secondary sites (horctakeover)NoNoNoYesNo

    * If both the copy source and the copy destination of the volumes for a UR pair are DP-VOLs, and the copy destination volume is set as the P-VOL of SI and Volume Migration (VM), you cannot create the UR pair. Release the SI and VM pairs, and then create a UR pair. After that, re-create the SI and VM pairs.

Configurations with SI secondary volumes

The following figure shows an SI primary volume used as the production volume. A remote UR backup copy is made of the SI secondary volume. The SI pair must be in PSUS status to perform the UR operation.

GUID-EF737350-1356-4852-A2A6-D1AFD240B8DD-low.png

In this configuration, before creating a UR pair, you must set the SI pair in the PAIR status, split the SI pair, and then set it in the PSUS status. The following table shows possibilities of UR pair operations according to the SI S-VOL status.

UR pair operations

SI S-VOL status

(VSP 5000 series) COPY(PD)/COPY

COPY(SP)/COPY

COPY(RS)/COPY

(VSP G/F350, G/F370, G/F700, G/F900, VSP E series)

COPY

PAIR

(VSP 5000 series) PSUS(SP)/PSUS

(VSP G/F350, G/F370, G/F700,G/F900, VSP E series)

PSUS(SP)

PSUS

PSUE

(VSP 5000 series)

COPY(RS-R)/RCPY

(VSP G/F350, G/F370, G/F700, G/F900, VSP E series)

RCPY

CreateNoNoNoYesNo
Split P-VOL specifiedNoNoNoYesNo
Split S-VOL specifiedNoNoNoYesNo
Resync P-VOL specifiedNoNoNoYesNo
Resync S-VOL specifiedNoNoNoNoNo
DeleteYesYesYesYesYes
Switch operations between the primary and secondary sites (horctakeover)NoNoNoNoNo

Pair status and data currency

The following table shows whether the data in a shared volume is current, given the combined status.

UR pair status

SI pair status

COPY(PD)/COPY

PAIR

COPY(SP)/COPY

PSUS

COPY(RS/COPY, COPY(RS-R)/COPY

PSUE

COPY

Not Current

Not Current

Not Current

Current

Not Current

Not Current

PAIR

Not Current

Not Current

Not Current

Current

Not Current

Not Current

PSUS/PSUE

Not Current

Current

Current

Current

Current

Not Current

Check pair status for shared volumes as follows:

  • For UR, check status of the primary volume or secondary volume.
  • For SI, check status of the primary volume.

SI supports multiple secondary volumes for each primary volume. When you check pair status, the system returns status for only one pair: the pair whose secondary volume has the lowest LDEV ID. To see status for the pairs with a different secondary volume, direct a host query to the specific secondary volume using the secondary volume’s LDEV ID in the host command.