News Column

Patent Issued for Methods of Writing and Recovering Erasure Coded Data

May 27, 2014



By a News Reporter-Staff News Editor at Information Technology Newsweekly -- A patent by the inventors Aguilera, Marcos Kawazoe (Palo Alto, CA); Janakiraman, Ramaprabhu (St. Louis, MO), filed on July 23, 2004, was published online on May 13, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8726129 is assigned to Hewlett-Packard Development Company, L.P. (Houston, TX).

The following quote was obtained by the news editors from the background information supplied by the inventors: "A critical component of computer systems is data storage. The data storage can be divided conceptually into an individual user's data storage, which is attached to the individual's computer, and network based data storage typically intended for multiple users.

"One type of network based storage device is a disk array. The disk array includes a controller coupled to an array of disks. Typically, each of the disks of the disk array is hot swappable, which allows a disk to be replaced without turning off the disk array.

"Often the network based storage must meet various performance requirements such as data access speed and data reliability. One way of providing high data access speed is to store data in stripes across multiple disks of the disk array. Each stripe includes multiple data blocks, each of which is stored on a separate disk. When the data is stored or read, each of the disks that holds a data block stores or retrieves the data block associated with it. In this way, the stripe of data is stored or retrieved in about the time it takes to store or retrieve one data block.

"One way of providing high reliability is data replication. For the disk array, the data replication stores one or more additional copies of data on one or more separate disks. If one of the disks holding a copy of the data fails, the data is still accessible on at least one other disk. Further, because of the hot swappable feature of the disk array, a failed disk can be replaced without turning off the disk array. Once the failed disk has been replaced, the lost copy of the data can be restored.

"Another way of providing the high reliability is erasure coding. Typically for the disk array, the erasure coding encodes one or more redundancy blocks for at least two data blocks stored on the device. Each of the data blocks and the one or more redundancy blocks is stored upon a separate disk of the disk array. If one of the data blocks is lost, it can be retrieved by decoding the lost data block from a redundancy block and the remaining data blocks.

"As an alternative to the disk array, researchers have been exploring data storage on an array of independent storage devices which form a distributed storage system. Each of the independent storage devices includes a disk and a network adapter. A potential advantage of the array of independent storage devices includes an ability to locate each of the independent storage devices in separate physical locations. Another potential advantage of the array of independent storage devices is lower cost. The lower cost can result from utilization of commodity components to construct the array of independent storage devices.

"What is needed is a method of writing erasure coded data in a distributed storage system."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "According to an embodiment, the present invention comprises a method of writing erasure coded data. In an embodiment, the method begins with a first step of swapping a new data block for an old data block within a stripe of erasure coded data. The stripe of erasure coded data comprises data blocks and a redundancy block. The method continues with a second step of computing a redundancy update parameter for the redundancy block using the new data block and the old data block. The method concludes with a third step of updating the redundancy block using the redundancy block, the redundancy update parameter, and a mathematical operator, thereby forming a new redundancy block.

"In another embodiment of the method of writing the erasure coded data, the stripe of erasure coded data comprises the data blocks and redundancy blocks. According to this embodiment, the method instantiates the third step for each of the redundancy blocks.

"According to another embodiment, the present invention comprises a method of recovering erasure coded data. In an embodiment, the method of recovering the erasure coded data begins with a first step of obtaining a lock on a subset of data blocks and one or more redundancy blocks. The data blocks and the one or more redundancy blocks comprise a stripe of erasure coded data. In a second step, the method determines whether the subset of the data blocks and the one or more redundancy blocks includes sufficient blocks to restore the stripe of erasure coded data. If the subset of data blocks does not include the sufficient blocks to restore the stripe of erasure coded data, the method relaxes the lock to allow at least one update of the one or more redundancy blocks while not allowing any writes of the data blocks in a third step. The method continues with a fourth step of using the subset of the data blocks and the one or more redundancy blocks to restore the stripe of erasure coded data. The method concludes with a fifth step of releasing the lock.

"These and other aspects of the present invention are described in more detail herein."

URL and more information on this patent, see: Aguilera, Marcos Kawazoe; Janakiraman, Ramaprabhu. Methods of Writing and Recovering Erasure Coded Data. U.S. Patent Number 8726129, filed July 23, 2004, and published online on May 13, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=17&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=822&f=G&l=50&co1=AND&d=PTXT&s1=20140513.PD.&OS=ISD/20140513&RS=ISD/20140513

Keywords for this news article include: Information Technology, Information and Data Storage, Information and Data Replication, Hewlett-Packard Development Company L.P..

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Source: Information Technology Newsweekly


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