Maximum number of failed disks supported by Erasure Code

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The maximum number of failed disks supported by Erasure Code is related to the M+N policy. The number of failed disks is smaller than N. If case of node failure, the maximum number of failed nodes supported by Erasure Code is N. If failed disks also exist, the maximum number of failed nodes supported by Erasure Code is smaller than N. For details, refer to the technical principles of Erasure Code.

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Principles and computing method of Erasure Code for OceanStor 9000
Erasure Code supports two data protection levels: N+M and N+M:B. N+M includes N+1, N+2, N+3, and N+4, and is suitable for scenarios with a large number of nodes. N+M:B includes N+2:1 and N+3:1, and is suitable for scenarios with a small number of nodes. N+M indicates that each data stripe contains N original data strips and M redundant data strips, ensuring high data integrity even when M nodes fail. N+M:B indicates that each data stripe contains N original data strips and M redundant data strips, ensuring high data integrity even when M disks or B nodes fail. Users only need to specify +M or +M:B for directories or files. OceanStor 9000 automatically selects the most appropriate N value based on the number of nodes. N ranges from 2 to 16, and M from 1 to 4. To configure the redundancy ratio: 1. Log in to DeviceManager. 2. Choose Provisioning > Resource Manager. 3. On the page that is displayed, select a directory and click Properties. 4. In the dialog box that is displayed, click the Redundancy Ratio tab and set +RDC/RDN. In N+M scenarios, data slices are stored on N nodes, and redundant data is stored on another M nodes. Among the N+M nodes, up to three are allowed to fail at the same time. However, N is within 2 to 16 and OceanStor 9000 supports a maximum of 288 nodes. Accordingly, some nodes (except the N+M nodes) do not store data slices, and the failure of these nodes, in theory, does not impact on data integrity. In N+M:B scenarios, data slices are stored on some disks of N nodes, and M pieces of redundant data are stored on other disks of the N nodes. The system allows up to M pieces of redundant data to be lost. That is, M disks are allowed to fail at the same time. Similarly, if more than B nodes fail, more than M pieces of redundant data will be lost. Therefore, a maximum of M disks or B nodes are allowed to fail.

How many disks does a VCN3000 support?
The VCN3000 supports 38 disk slots, including thirty-six 3.5-inch service disks and two 2.5-inch operating system disks.

Code (RS, Raptor, or others) used by Erasure Code of OceanStor 9000
Huawei develops Erasure Code of OceanStor 9000 based on the array code and has the patent and intellectual property of the Erasure Code algorithm.

Storage products using erasure coding
Erasure coding (EC) is a general algorithm for data distribution and redundancy protection. The application scenarios include storage, arrays, and cloud storage.

Maximum number of disk domains supported by 5300 V3
The OceanStor 5300 V3 storage system V300R001 supports a maximum of 32 disk domains. For detailed specifications, see V3R1 Latest Software Specifications.

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