Synology DS1821 Synology High Availability s White Paper - Page 12

Best Practices for Deployment Best Practices for Deployment Different customers of Synology NAS products may attach importance to various aspects of practices according to their needs and purposes. Here, we provide the best practices regarding system performances and reliability respectively. These two types of configuration are not mutually exclusive. You may apply both practices to optimize the overall system environment. Before the configuration, make sure that your system environment complies with the basic requirements for Synology High Availability. Both servers must be of the same model, and with the identical configuration including the capacity, quantity, and slot order of drives and RAM modules. Aside from the drive and RAM module configuration, both servers must have the same number of attached network interface cards and LAN ports. System Performances To meet the needs of operating performance-intensive services, and of processing a massive amount of connections or frequent data access for a long time, you can optimize the performances with the following configuration: SSD Cache SSD cache brings a significant rise in data reading and writing speeds of the system, especially under the circumstance where the data storage consists of hard disk drives (HDD). Since solidstate drives (SSD) are specifically designed for high performance usage, by promoting frequently accessed data into SSDs, one can fully utilize the system's random I/O access to effectively reduce the latency and extra data seek time as on HDDs. SSD cache must be configured in the identical configuration and each SSD must be inserted in the same disk slot in both the active server and passive server. The size of system memory needs to be identical on the active and passive servers as partial memory needs to be allocated for operating SSD cache. Therefore, different memory sizes may result in unavailability of system failover. The failover mechanism is also applied on SSD cache. This means, when the SSD cache on the active server fails, a system failover to the passive server will be triggered. Fast Heartbeat Connection When data is transferred to the HA cluster, the copy of such data will be transferred to the passive server through the heartbeat connection at the same time. The writing process is complete only when both transfers finish. In this case, if a Gigabit network environment is applied, the writing speed will be limited to 1Gbps by the network environment. Most plus-series and all FS/XS-series are equipped with the capability of adding additional external network cards for additional high-speed network interfaces (e.g. 10Gbps). The most basic principle of network settings for a High Availability cluster is that the heartbeat connection bandwidth must be greater than or equal to the cluster network interface. Heartbeat connection is one of the fastest network interfaces, including link aggregation or 10G/40G network interface. Synology offers optional 10GbE external network interface cards to be used with High Availability cluster. When working with multiple external network interface cards, link aggregation must be set up interchangeably to increase fault tolerance. Please refer to the following environment setup examples. Setup with Single-Volume Storage Pool When using a single-volume storage pool, the system avoids the impact on system performances from the LVM (logical volume management) coming with a multiple-volume storage pool. We highly recommend the setup with single-volume storage pool for the peer-to-peer storage architecture of Synology High Availability. Synology White Paper 11