Synology DS1821 Synology High Availability s White Paper - Page 13

Best Practices for Deployment Reliability Synology High Availability is dedicated to the hardware and software protection of Synology NAS servers. However, aside from the NAS storage itself, the normal operation of the whole services also depends on a couple of other factors, including stable network connections and power supply. Direct Heartbeat Connection between Two Servers When the heartbeat connection between the active and passive servers goes through a switch, it increases the difficulty in managing the risk of network failure caused by the switch per se or the connections from the switch to the respective servers. When you take into consideration the reliability of your system, it is recommended to make a direct heartbeat connection between the active and passive servers. Heartbeat and HA Cluster Connections with Link Aggregation A link aggregation is formed by at least two connections between the same peers. It not only increases transfer rates, but enhances the availability of such network connections. When one of the interfaces or connections in a link aggregation fails, the link will still work with the rest. In this section, we provide an anvironment setup scenario as follows. Two RS4017xs+ models are each equipped with two E10G17-F2 external network interface cards. There are four 1GbE network interfaces (local network 1, 2, 3, 4) and four 10GbE network interfaces (local network 5, 6, 7, 8) on each NAS. Local network 5 and 6 are provided by external network interface card 1, and local network 7 and 8 are provided by external network interface card 2. Please refer to the recommended setup below: • Heartbeat interface: Link Aggregation of the 10GbE network interface. One interface from external network interface card 1 and one interface from external network interface card 2. • Cluster interface: Link Aggregation of the 10GbE network interface. One interface from external network interface card 1 and one interface from external network interface card 2. These configurations ensure the performance of both cluster connection and Heartbeat connection is maximized while maintaining redundancy for both connections. The network service provided by the cluster will not be affected by the Heartbeat connection, thus increasing fault tolerance for the external network interface card. In the case that a problem occurs with external network interface card 1, all services can still be provided through external network interface card 2. To prevent slow writing speed due to the process of replicating data to the passive server when data is written, it is recommended that the Heartbeat connection is of the same or higher bandwidth as the service. The Heartbeat connection must be configured on the fastest network interface. For instance, if the servers are equipped with 10GbE add-on network cards, the Heartbeat connection must be configured by using 10GbE cards. In addition, it is strongly recommended that users build a direct connection (without switches) between two servers, the distance between which is usually shorter than 10 meters. If a HA cluster requires two servers with a larger distance, the Heartbeat connection between two servers must have no other device in the same broadcast domain. This configuration can be achieved by configuring a separate VLAN on the Ethernet switch to isolate the traffic from other network devices. Please make sure that cluster connection and Heartbeat connection are in different loops lest they be interrupted at the same time when functioning. Separate Switches for the Cluster Connections Network switch is required for the HA cluster connection between the active/passive server and the client computer. To avoid network switch malfunctions, we recommend connecting each of the two servers to a different switch. For example, you can set up a link aggregation with two connections between one switch and the active server, and set up another one between another switch and the passive server. Then, the client computer will be configured with two connections, each of which is linked to one of the two switches. Separate Power Supply for Servers and Switches Aside from the reliability of network connections among the servers, switches, and clients, we are also supposed to take into consideration the stable power supply for the system. Most FS/ XS-series and plus-series with RP are equipped with redundant power supply, allowing you to allocate different electric power sources to the server. For the NAS models without redundant power supply, we recommend allocating a power supply to one server and its connected switch, and another one to the other server and switch. This helps mitigate the risk of system failure resulting from power outage of both servers/switches. 12 Synology White Paper