Update copy workflow

ShadowImage User Guide

Part Number

Update copy is performed to asynchronously copy new data (differential data) from the P-VOL of a copy volume to the S-VOL.

The storage system goes through the following process to create an update copy:

  1. The storage system marks I/O to the P-VOL in PAIR status as differential data and stores the location of the data in bitmaps for transfer to the S-VOL.
  2. After there are write I/O operations to a P-VOL, the storage system starts the update copy operation.
    Note: The timing of the update copy operation is based on the amount of differential data that accumulates and the elapsed time since the previous update.

The following image shows the update copy operation.

Updated data is copied asynchronously. Therefore, even when the initial copy completes and the pair status changes to PAIR, data in the P-VOL and in the S-VOL might not be the same. If you want data in the P-VOL and in the S-VOL to match at a certain date and time, you must split the pair.

Note: Data in the P-VOL and in the S-VOL might not be the same if the host did not write data to the P-VOL during copy operation. To ensure matching data in the P-VOL and the S-VOL, you must split the pair to change its status to PSUS.