News Column

Patent Issued for Ensuring Write Operation Consistency Using Multiple Storage Devices

June 17, 2014



By a News Reporter-Staff News Editor at Journal of Technology -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Gupta, Nitin (Fremont, CA); Vijayasankar, Kiron (Sunnyvale, CA); Berry, Joshua (El Cerrito, CA), filed on May 4, 2012, was published online on June 3, 2014.

The assignee for this patent, patent number 8745320, is Riverbed Technology, Inc. (San Francisco, CA).

Reporters obtained the following quote from the background information supplied by the inventors: "This disclosure relates generally to data storage systems, and systems and methods to improve storage efficiency, compactness, performance, reliability, and compatibility. Magnetic disk storage devices, such as hard disk drives, provide large amounts of affordable storage. However, magnetic disk storage devices often include an internal write buffer for storing write data before it is written to disk. Write data stored in the internal write buffer is at risk of loss if there is a power failure. Magnetic disk storage devices may be configured so that write operations are only acknowledged after the write data has been stored on disk, as opposed to the internal write buffer; however, this reduces write performance greatly. More specialized hardware, such as hardware RAID controllers, may include battery or supercapacitor power backups to preserve data in the write buffer in the event of a power failure; however, these hardware components increase the cost and complexity of systems.

"In contrast, many relatively low-cost solid-state disk drives (SSDs) include a backup power source, such as a battery or supercapacitor, to preserve write data in the write buffer in the event of a power failure. However, SSDs are much more expensive than magnetic disk drives of similar storage capacity. Thus, most low-cost SSDs have much smaller storage capacities than typical magnetic disk drives."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "Embodiments of the invention combine a relatively small capacity solid-state storage device (SSD) to ensure data consistency in the event of a power failure or other problem with a larger capacity magnetic disk storage device for storing storage block write data. Embodiments of the invention first store write operation in a sequential write buffer in an SSD to guarantee the storage of write data and then copy write data from the sequential write buffer to the desired storage location in a magnetic disk storage device.

"In an embodiment, the SSD guarantees the storage and consistency of any write operation that is received and acknowledged by the SSD. An embodiment of the invention receives write operations from storage clients. The write operations include write data and a destination address. The embodiment of the invention stores a page including at least the write data and the destination address in a sequential guaranteed write buffer in the SSD. The sequential guaranteed write buffer stores pages in locations corresponding to the order of receipt of write operations, rather than according to their destination addresses. Additionally, the SSD guarantees the consistency of any pages stored in the sequential guaranteed write buffer.

"In addition to storing pages in the sequential guaranteed write buffer, an embodiment of the invention also transfers at least the write data from pages to their respective destination addresses in a magnetic disk storage device. Unlike the SSD, the magnetic disk storage device may not guarantee write operations. However, the magnetic disk storage device typically provides much higher storage capacity than an SSD of similar price. Write data from the sequential guaranteed write buffer is transferred to the magnetic disk storage device in the same order as their corresponding write operations were received. Additionally, an embodiment of the invention frequently updates a checkpoint index value to indicate that a portion of the pages in the sequential guaranteed write buffer have been successfully transferred from the SSD to the magnetic disk storage device.

"In an embodiment, during system initialization following a power failure or any other system downtime, the most recent value of the checkpoint index is retrieved. An embodiment of the invention begins transferring write data from the sequential guaranteed write buffer to the magnetic disk storage device from the buffer location corresponding with the checkpoint index value. This transfer continues until the write data from all of the pages in the sequential guaranteed write buffer that may not have been processed earlier are transferred to the magnetic disk storage device. At this point, all of the write operations guaranteed by the SSD have been successfully transferred to the magnetic disk storage device. Meanwhile, during system initialization, embodiments of the storage system may receive and store additional write operations once the buffer locations of the checkpoint index and the most-recently accepted write data have been identified."

For more information, see this patent: Gupta, Nitin; Vijayasankar, Kiron; Berry, Joshua. Ensuring Write Operation Consistency Using Multiple Storage Devices. U.S. Patent Number 8745320, filed May 4, 2012, and published online on June 3, 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=8745320.PN.&OS=PN/8745320RS=PN/8745320

Keywords for this news article include: Riverbed Technology Inc..

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Source: Journal of Technology


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