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A method for reading data from mirrored flash storage system.

IP.com Disclosure Number: IPCOM000249042D
Publication Date: 2017-Jan-30
Document File: 3 page(s) / 58K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a system to the reading of data from a flash storage. In the reading of the data saved in multiple flash storages, the timing of the internal background process to be executed by a certain flash storage is dynamically changed such that the collision with the other flash storages is prevented, and thereby, the decrease in transfer speed is avoided.

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A method for reading data from mirrored flash storage system.

The present invention relates to the reading of data from a flash storage.

As a method for saving data in multiple storages, there is a technique called RAID1 (mirroring). When data is written in mirrored storages, the data is saved in the multiple storages. In the case where the data is read from the mirrored storages, a read command, typically, is issued to the multiple storage media in which the data is stored. Then, the first read data is sent to the host, and the second or later read data is discarded with no change.

Unlike hard disks, the flash storage needs to erase written data in several-kilobyte units, which are called blocks. Therefore, for eliminating fragments, a series of internal background processes are required. Specifically, data in a block is read, all data in the block is erased, only the necessary data in the block is written afresh, and the other area is used for future writing. Naturally, when such internal background processes occur during the writing of data, the transfer speed temporarily decreases.

Hereinafter, an embodiment of the present invention will be described. The embodiment will be described with an eye on the case where flash storages are used while being mirrored. However, the present invention can be applied also to non-mirrored flash storages.

Conventionally, mirrored flash storages operate independently. In the present invention, the mirrored flash storages cooperate with each other, and each flash storage monitors the behaviors of the other flash storages, and changes the action depending on the behaviors of the other flash storages. More specifically, the changing of the timing of the execution of the internal background process is proposed. For example, each flash storage postpones the execution of the internal background process while the other flash storages are executing the internal background process, and thereby, it is possible to avoid the multiple flash storages from executing the internal background processes simultaneously. When it is possible to avoid the multiple flash storages from executing the internal background processes simultaneously, it is possible to ensure that at least one flash storage is not executing the internal background process, in the reading of data from the mirrored flash storages. Therefore, it is possible to constantly read data at a high speed.

One of the internal background processes in the flash storage is a garbage collection. At the time of the writing of data, the flash storage writes the data in units of a cell. On the other hand, at the time of the erase of data, the flash storage, as the feature, can perform the erase only in units...