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The configuration information of an NFS export mainly includes its name, the storage policy, and access settings.
A storage policy includes settings for the number of replicas and the provisioning type. The storage policy in an NFS export determines the storage policy applied to newly created NFS files within that export.
Replication:
Replication technology involves storing multiple replicas of the same data across several nodes to ensure high data availability. It provides redundancy, so if one node fails, other healthy nodes still have complete replicas to ensure normal I/O operations.
An NFS export allows for a replication factor of two or three. By default, a replication factor of three is used when there are at least five nodes available for storage services; otherwise, a replication factor of two is used. If the cluster has the active-active clustering feature enabled, only a replication factor of three is supported.
Erasure coding:
Erasure coding (EC) is a data redundancy mechanism. It uses a specific algorithm to process K original data blocks and generate M parity blocks. As long as the number of damaged data blocks does not exceed M, the erasure coding algorithm can reconstruct the damaged blocks using the available K data blocks and parity blocks, ensuring data recovery and fault tolerance. With erasure coding, even if some data is lost, the complete data can still be restored, significantly improving storage system reliability and space utilization.
Note:
To enable erasure coding, the cluster must meet the following requirements:
- The number of healthy nodes in the cluster is not less than 4;
- The cluster adopts the tiered-storage mode;
- The cluster is not an active-active cluster.
The provisioning type is a storage space allocation policy. An NFS export supports both Thick provisioning or Thin provisioning.
Thick provisioning:
With thick provisioning, the system immediately allocates all the specified space for an NFS file upon creation, even if the file is only using a portion of that space. The entire allocated space remains occupied by the file and cannot be used by other resources.
Thin Provisioning:
With thin provisioning, the system does not immediately allocate all the specified space for an NFS file upon creation. Instead, it dynamically allocates space as needed. It only allocates actual storage when data is written. Until data is written, the storage space remains unoccupied.
You can configure an IP allowlist for an NFS export, allowing only clients listed in the allowlist to access that NFS export. The IP allowlist can be set to Ban all, Specify IP, and Allow all. The default is Allow all.