| 摘要 |
The invention provides for remote copying, between peer storage systems, with data extent granularity. A compressed data image is read from a first location of a primary storage volume. Metadata, and then the compressed data image, are transferred to a secondary storage volume. The metadata specifies a first location within the primary storage volume and a second location within the secondary storage volume. The compressed track is then stored into a second location of the secondary volume. A host connected to the primary control unit specifies data extents within the primary and secondary volumes. The data extents specify the first and second locations, and more preferably define cylinder information, track information, and start and end addresses. An "Establish Pair" command can be used to specify the data extents. A seed value can be used with the metadata to identify the data image during subsequent decompression of the data image in the secondary storage volume. If count fields are used, the secondary control unit modifies the field to specify the correct cylinder and head number at the location of the secondary extent.
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