News Column

Patent Issued for Remote Copy System and Remote Copy Control Method

July 8, 2014



By a News Reporter-Staff News Editor at Information Technology Newsweekly -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Hara, Junichi (Sagamihara, JP); Ogawa, Junji (Sagamihara, JP), filed on December 8, 2011, was published online on June 24, 2014.

The assignee for this patent, patent number 8762638, is Hitachi, Ltd. (Tokyo, JP).

Reporters obtained the following quote from the background information supplied by the inventors: "In a remote copy operation, a line (for example, a line of a WAN (Wide Area Network) managed by a telecommunications vendor may be leased, and remote copying may be performed between storage systems by way of this leased line. For this reason, when the amount of data being sent and received between the storage systems increases, communications charges rise proportionally. These communications charges account for a large percentage of the costs involved in operating a remote copy system. Therefore, the smaller the amount of data sent and received between storage systems the better.

"One method for reducing communications charges is to compress the data sent from the one storage system to the other storage system. However, the problem is that for a storage system, which does not comprise a data compression function, an appliance (a dedicated device) for compressing and sending data must be purchased and installed separately from the storage system, which is both costly and time consuming.

"Another problem is that even though an appliance is purchased and installed, it is not possible to compress the data to be sent beyond expectations (that is, the data amount cannot be reduced very much). This is because the extent to which the data amount can be compressed depends on the type of data being sent, and until the appliance is actually operated, there is no way of identifying the type of data being handled. For example, in a case where the data to be sent is JPEG (Joint Photographic Experts Group) data, the JPEG data cannot be compressed much because it is already compressed.

"Alternatively, there are storage systems, which use a storage device comprising a data compression function (for example, a SSD (Solid State Drive)). The SSD compresses write-target data, partitions the compressed data on the basis of the size of a page, which is the read/write unit, and writes the partitioned data to a page together with a guarantee code (for example, an ECC (Error Correcting Code)) for each write-destination page (Patent Literature 1)."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "Technical Problem

"However, in a case where compressed data has been read from an FM chip, the SSD restores (decompresses) and outputs this data. For this reason, even though an SSD is used as the storage device in the storage system, the amount of data being sent and received between the storage systems is unable to be reduced.

"This problem is not limited to the SDD, but can also occur in a case where another type of storage device comprising a data compression function (for example, a HDD (Hard Disk Drive)) is used.

"Therefore, an object of the present invention is to enable the amount of data being sent and received between storage systems to be reduced even though a storage device comprising a data compression function is being used as the storage device in the storage system.

"Solution to Problem

"In a remote copy system comprising a first storage system, and a second storage system, which is coupled to the first storage system by way of a communications network, the first storage system comprises a first RAID group comprising multiple first storage devices, which constitute the basis of a first logical volume, and a first controller, which is coupled to the first RAID group. The second storage system comprises a second RAID group comprising multiple second storage devices, which constitute the basis of a second logical volume, and a second controller, which is coupled to the first controller and the second RAID group.

"The RAID configuration of the first RAID group and the RAID configuration of the second RAID group are the same, each first storage device configuring the first RAID group comprises a first compression/decompression function for compressing write-target data and for decompressing read-target compressed data, and each second storage device configuring the second RAID group comprises a second compression/decompression function for compressing write-target data and for decompressing read-target compressed data. The type of the second compression/decompression function is the same as the type of first compression/decompression function.

"In a case where a first remote copy, which is a remote copy of data from the first logical volume to the second logical volume, is performed:

"(A) compressed data is read from each first storage device in accordance with the first controller sending a read request to each first storage device configuring the first RAID group for reading the compressed data without performing decompression with respect to data inside the first logical volume; and

"(B) the read compressed data is transferred to the second controller by way of the communication network for each first storage device, and the compressed data is written to an area corresponding to the second logical volume of a second storage device in accordance with the second controller sending a write request for writing the compressed data without performing a compression to this second storage device, which is in the same location in RAID in the second RAID group as the location in RAID of the first storage device.

"The location in RAID is the location of the storage device in the RAID group."

For more information, see this patent: Hara, Junichi; Ogawa, Junji. Remote Copy System and Remote Copy Control Method. U.S. Patent Number 8762638, filed December 8, 2011, and published online on June 24, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8762638.PN.&OS=PN/8762638RS=PN/8762638

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

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Source: Information Technology Newsweekly


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