News Column

Researchers Submit Patent Application, "Logical Volume Transfer Method and Storage Network System", for Approval

July 1, 2014



By a News Reporter-Staff News Editor at Information Technology Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Satoyama, Ai (Kanagawa, JP); Eguchi, Yoshiaki (Kanagawa, JP); Yamamoto, Yasutomo (Kanagawa, JP), filed on February 17, 2014, was made available online on June 19, 2014.

The patent's assignee is Hitachi, Ltd.

News editors obtained the following quote from the background information supplied by the inventors: "This invention relates to a storage control unit having a plurality of control devices connected to a plurality of disk devices, and method of transferring replication logical volumes thereof.

"As a virtualization art concerning logical volumes of a storage control unit, there is an art of managing logical units (LU) of an external storage control unit, which is of a different frame from the unit, inside the storage control unit. See, for example, Japanese Patent Application Laid-Open (Kokai) Nos. H7-210439, 2001-318833 and 2003-008821. There are also arts for creating replications of logical volumes inside a storage control unit.

"In recent years, a concept called 'storage grid,' with which a plurality of distributed computing resources are put into operation as a single entity, is becoming noted in the storage industry. As one form thereof, a configuration may be considered wherein a plurality of storage control units are arranged together and deemed to be a single system. Presently, the data in replication logical volumes (including relevant volumes, such as those of the same attribute, etc.) in a storage control unit cannot be transferred with the relevance being maintained to other storage control units in accompaniment with an increase or decrease of the number of storage control units or for the purpose of load distribution between and among storage control units. Furthermore, in cases where the abovementioned storage control units are connected to an external storage control unit, logical volume transfer processes between and among storage control units cannot be performed likewise for replication logical volumes that are entities in the external storage control unit.

"This invention has been made in view of the above issues and aims to provide in a storage system comprising a plurality of storage control units, a means for transferring replication logical volumes (including those with which the logical volume entities exist in an external storage control unit) between and among storage control units."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "In order to achieve the above object, this invention provides a logical volume transfer method, whereby, in a system comprising: a storage system, having logical volumes, logically managed by a plurality of storage control units, as entities in the respective storage control units or in an external storage control unit connected to the storage control units; and a virtualization device, identifying the plurality of storage control units as a single storage control unit; the logical volumes are transferred between and among the storage control units, wherein in transferring the logical volumes among the storage control units, other logical volumes, forming a pair or a group of two or more pairs with the logical volumes, are transferred includingly.

"The logical volume transfer method according to this invention is characterized in including, in case the logical volume comprise replication logical volumes, the entities of the replication logical volumes exist in the external storage control unit, and the primary logical volume and the secondary logical volume of the replication logical volumes are to be transferred from a first storage control unit with which a path to the virtualization device is already set, to a second storage control unit with which the path is not set, the steps of: the virtualization device setting a path to the second storage control unit; the second storage control unit preparing differential bitmaps, indicating the data difference between the primary logical volume and the secondary logical volume, in order to receive access requests; the virtualization device, upon completion of the preparation of the differential bitmaps, making a setting so that access requests of the logical volumes are made not to the first storage control unit but to the second storage control unit; the second storage control unit handing over the access requests received from the virtualization device to the first storage control unit; the first storage control unit processing the access requests received from the second storage control unit so as to reflect the access requests in a disk device; the first storage control unit performing an emergency destage for storing the data in a cache memory of the logical volumes into the disk device; and the second storage control unit, upon completion of the emergency destage, connecting to the external storage control unit and handing over access requests received from the virtualization device to the external storage control unit instead of the first storage control unit,

"It is to be noted that a 'virtualization device' in the Claims corresponds to a 'virtualization program or virtualization device 52 in a host 51' as discussed in description of the preferred embodiments. This invention also includes logical volume transfer methods and a storage network system other than those described herein.

"The present invention has an effect of allowing transferring replication logical volumes between and among storage control units, in a storage system comprising a plurality of storage control units. The replication logical volumes include those with which the logical volume entities exist in an external storage control unit.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a diagram showing the general configuration of a storage system of an embodiment of this invention.

"FIGS. 2A and 2B are diagrams each showing an 'exemplary configuration of a service processor.

"FIG. 3 is a diagram showing a configuration of an exchange path software;

"FIG. 4 is a diagram showing a memory configuration of a storage control unit;

"FIG. 5 is a diagram showing an example of a same-device correspondence table;

"FIG. 6A is a diagram showing an exemplary volume pair information management table for creating a replication in the same storage control unit;

"FIG. 6B is a diagram showing an exemplary volume pair information management table for creating a replication across different storage control units;

"FIG. 7 is a diagram showing an example of a volume information table;

"FIG. 8A is a diagram showing a differential bitmap in an example, where one differential bitmap is prepared;

"FIG. 8B is a diagram showing a differential bitmap in an example, where two bitmaps of the same size are prepared for a single pair;

"FIG. 9A is a diagram showing differential bitmap configuration across storage control units, in a one-bitmap configuration;

"FIG. 9B is a diagram showing differential bitmap configuration across storage control units, in a two-bitmap configuration;

"FIG. 10 is a flowchart illustrating a process prior to transferring a pair of logical volumes between storage control units;

"FIG. 11 is a flowchart illustrating a process for starting the transfer of a pair of logical volumes between storage control units;

"FIG. 12 is a flowchart illustrating a pre-transfer process in case a storage control unit is added;

"FIG. 13 is a flowchart illustrating a pre-transfer process in case a storage control unit is eliminated;

"FIG. 14 is a flowchart illustrating a pre-transfer process in case logical volume transfer across a plurality of storage control units is to be performed for the purpose of load distribution;

"FIG. 15 is a diagram showing a configuration and an I/O pathway that takes note of the logical volumes of a pair to be transferred;

"FIG. 16 is a diagram showing a configuration and an I/O pathway that takes note of the logical volumes of a pair to be transferred;

"FIG. 17 is a diagram showing a configuration and an I/O pathway that takes note of the logical volumes of a pair to be transferred;

"FIG. 18 is a flowchart illustrating a process for transferring a primary logical volume of a pair of logical volumes between storage control units; and

"FIG. 19 is a flowchart illustrating a process for transferring a secondary logical volume of a pair of logical volumes between storage control units.

"FIG. 20 is a diagram showing an example of a group information table.

"FIG. 21A is a diagram showing a method for performing a Split request from a host when a group is stored in one storage control unit, wherein an At-Time Split command is published to the group.

"FIG. 21B is a diagram showing a method for performing the Split request from the host when the group is stored in one storage control unit, wherein the At-Time Split command is published to one of the pairs in the group.

"FIG. 22A is a diagram showing a method for performing the Split request from the host to all of a plurality of storage control units when the group exists across the plurality of units, wherein the At-Time Split command is published to the group.

"FIG. 22B is a diagram showing a method for performing the Split request from the host to all of a plurality of storage control units when the group exists across the plurality of units, wherein the At-Time Split command is published to one of the pairs in the group.

"FIG. 23 is a diagram showing transfer and splitting processes for a replication logical volume when the host includes the group information table.

"FIG. 24 is a diagram showing an example of the address mapping table.

"FIG. 25 is a diagram showing a construction to achieve a method for including the primary volume and the pool area in an external storage control unit."

For additional information on this patent application, see: Satoyama, Ai; Eguchi, Yoshiaki; Yamamoto, Yasutomo. Logical Volume Transfer Method and Storage Network System. Filed February 17, 2014 and posted June 19, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=553&p=12&f=G&l=50&d=PG01&S1=20140612.PD.&OS=PD/20140612&RS=PD/20140612

Keywords for this news article include: Hitachi Ltd., Information Technology, Information and Data Management.

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Source: Information Technology Newsweekly


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