Method for building array by adding mirror image structure to check-based RAID and read-write system

Abstract

The invention discloses a method for building an array by adding a mirror image structure to a check-based RAID and read-write system. The method comprises the four steps of address layout, data layout, data access and data reconstruction. The read-write system comprises an I / O module, a mirror image management module, an address mapping module and the check-based RAID module. On the basis of the check-based RAID, the mirror image structure is added, so that the I / O performance of the array is improved; the reconstruction time is shortened by using mirror image data reconstruction; the novel address layout mode puts original data and mirror image data at the adjacent positions as much as possible, and the movement distance of a head is shortened; checking information is updated in the background, the write amplification problem of the check-based RAID is relieved, and the write performance of the array is improved; as the mirror image data exist, the fault-tolerant ability of the array is improved, and the availability and reliability of the array are greatly improved.

Description

technical field [0001] The invention belongs to the technical field of data storage, and more specifically relates to an array construction method and a read-write system based on a verification RAID and adding a mirror structure. Background technique [0002] Redundant Arrays of Independent Disks (Redundant Arrays of Independent Disks, RAID) has been widely used in large-scale distributed parallel storage systems because of its performance and reliability. In terms of performance, RAID achieves high throughput through striping. In terms of reliability, RAID uses redundant data such as mirroring or checksums to improve reliability. [0003] RAID can be divided into three types according to its redundant structure. First, there is no redundant structure. The representative array is RAID0. RAID0 uses data stripping technology (Data stripping) to disperse data to all disks, so that disks can be operated in parallel, which improves the read and write speed. The remaining struc...

AI Technical Summary

Problems solved by technology

First, there is no redundant structure. The representative array is RAID0. RAID0 uses data stripping technology (Data stripping) to disperse data to all disks, so that disks can be operated in parallel, which improves the read and write speed. Its space utilization rate is the highest in the array structure, but it also leads to its low reliability. Any disk failure in the array will cause the entire system to be damaged.

Second, based on parity RAID, the representative array is RAID5. RAID5 also uses data striping technology to store data in all disks in blocks, so that the disks can be operated in parallel. Unlike RAID0, Each stripe has a parity value, and all parity values ​​are evenly distributed among all disks, which has the advantage of improving reliability. If any disk in the array fails, the system can calculate it based on the remaining disks. The data of the failed disk; due to the addition of the redundant structure, the space utilization rate has decreased, and its redundant structure requires a total capacity of one disk. At the same time, due to its redundant structure, it leads to the problem of write amplification, that is, a write operation , will generate four actual IO operations, including two reads and two writes; in the reconstruction mode, it is necessary to read the data of all remaining disks to calculate the data of the faulty disk; in the degraded mode, the request to access the faulty disk is broken down into multiple I / O requests, which will result in long refactoring times, degraded mode, and low I / O performance in refactored mode

Third, mirror-based RAID. The representative array is RAID1. RAID1 is also called disk mirroring. It mirrors the data of one disk to another disk. Since the data is copied on different disks, I / O offloading can be realized. , so that access can be evenly distributed in the mirror, and if any disk in the array fails, the data will not be lost. The request to access the faulty disk can be directly converted into the request to access its mirror disk, and will not be decomposed into multiple I / O, and can directly read the data of the mirror disk corresponding to the faulty disk during reconstruction, the reconstruction time is short, and the I / O performance is high, but its space utilization rate is poor, and only half of the array capacity can be used

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