Description

Traditional network protocols (such as TCP and IP) are not designed for high-performance application scenarios and are unable to provide efficient communications. In this case, we use Remote Direct Memory Access (RDMA), the first network communication protocol used in high-performance computing, which enables computers to transfer data directly to each other’s memory without the intervention of the operating system, significantly reducing transmission latency and improving communication efficiency. Currently, RDMA is widely used in storage area networks, big data, and cloud computing with its zero-copy, kernel bypass, CPU offload, and low latency features.

RDMA is applied to the storage area networks of virtual storage platforms and is mainly deployed in the storage client and server processes to provide a mechanism similar to TCP for cross-node network communication. The RDMA feature can replace TCP for data transmission, lowering the network latency between the storage client and the server and dramatically increasing their throughput, which significantly improves the performance of virtual storage platforms.

Precautions

To enable RDMA, the storage switch must be configured with a congestion control algorithm; otherwise, business services may encounter network congestion during off-peak hours.

Enabling or disabling the RDMA feature requires business service interruptions (i.e., shutdowns of VMs and network devices, disconnections from iSCSI targets). Please perform this operation during off-peak hours.

Please make sure that the model of the storage adapter and its firmware version support RDMA. To query the adapter models and firmware versions supported by RDMA (passed the beta test), go to the adapter vendor’s official website or Sangfor HCI Compatibility Chart via: https://www.sangfor.com/cloud-and-infrastructure/products/hci-compatibility-chart.

RDMA cannot be enabled in 2+1, 2-node clusters, interface multiplexing, and stretched cluster scenarios.

RDMA cannot be enabled when HCI is connected to an ISCSI storage.

It is not supported for VMs running across datastores to use RDMA to access virtual storage (normal access is not affected). If VMs are scheduled to run on nodes associated with other datastores, business service performance will not be optimal, but better than RDMA disabled.

RDMA can only be enabled or disabled for two datastores associated with a node at the same time. If the number of nodes associated with these two datastores is not the same, you need to enable RDMA for the datastore that is associated with more nodes first, while the another datastore inherits the feature at the same time. This restriction does not apply to nodes associated with more than two datastores.

Enabling RDMA consumes no memory on nodes with 8 hard disk slots or less, but 2 GB of memory on nodes with 24 hard disk slots.

The storage network interface of a node that is replaced or added to a storage pool with RDMA enabled must support RDMA.

Steps

Go to Storage > Virtual Storage > Advanced > RDMA to enable RDMA for a virtual datastore. You can click View Compatibility to view whether the adapter models and the firmware versions of the storage network interfaces support the RDMA feature.