| US 7,454,583 B2 | ||
| Storage controller and control method for dynamically accomodating increases and decreases in difference data | ||
| Ikuya Yagisawa, Machida (Japan); Koji Nagata, Kaisei (Japan); and Shoji Kodama, Sagamihara (Japan) | ||
| Assigned to Hitachi, Ltd., Tokyo (Japan) | ||
| Filed on Mar. 07, 2006, as Appl. No. 11/368,423. | ||
| Claims priority of application No. 2006-005423 (JP), filed on Jan. 12, 2006. | ||
| Prior Publication US 2007/0162716 A1, Jul. 12, 2007 | ||
| Int. Cl. G06F 12/00 (2006.01); G06F 13/00 (2006.01); G06F 13/28 (2006.01) | ||
| U.S. Cl. 711—162 | 17 Claims |
| 1. A first storage controller which holds write data provided from a host system and duplexes said data in a second storage
controller, comprising:
a storage device which provides a storage area for storing data; and
a controller,
wherein said controller:
configures a production volume and a pool volume on said storage area,
sequentially stores said data provided from said host system into said production volume,
sequentially creates a snapshot composed of a data image of said production volume at a given point in time at regular or
irregular intervals, and
when said data is written in said production volume after said snapshot is created, sequentially saves the original data that
is contained in said production volume immediately prior to the write of said data into said pool volume as difference data
as appropriate, and
after creating a new version of said snapshot, sequentially reads said difference data of said previously created snapshot
from said pool volume and transfers said difference data to said second storage controller, and
wherein said controller further:
configures a plurality of said pool volumes,
assigns a first pool volume out of a plurality of said pool volumes to a first copy pair,
assigns a second pool volume to both of a second and third copy pairs,
wherein each of said copy pairs includes a group of related production volumes and its corresponding secondary volume contained
in the second storage controller, or includes one of said production volumes that does not belong to the group of related
production volumes and its corresponding secondary volume contained in the second storage controller,
creates said snapshot for each of said copy pairs regularly and changes cycle time as appropriate, said cycle time being a
time interval during which said snapshot is created,
obtains, for each of said copy pairs, a time difference between the time of creation of said snapshot and the time of completion
of transfer of said snapshot to said second storage controller, and
dynamically changes said cycle time for each of said copy pairs in accordance with said time difference,
wherein when the time difference is greater than a predetermined first threshold value, the controller increases said cycle
time for each of said copy pairs, and
wherein when the time difference is less than a predetermined second threshold value, the controller decreases said cycle
time for each of said copy pairs.
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