Most administrators want their individual servers to be highly available, but it’s really the services that need to be highly available. In a large RDS deployment, if you are implementing eight RD Session Host servers, this would save $8,000 in hardware costs, which you could use to purchase two or three additional servers to provide high availability. In the previous example, you could save $1,000 per server by not putting in dual power supplies and hardware RAID cards. This can be a cost-effective way to provide high availability.
Instead of providing hardware redundancy in servers, you can provide the redundancy with additional servers. When you have highly available infrastructure with multiple servers, you can balance the high availability of components within a server with the high availability provided by having multiple servers. Combined, these options can add $1,000 to the cost of a server. Within a server, two common hardware components for high availability are dual power supplies and hardware RAID cards. Some RDS role services require you to implement load balancing. To make RDS highly available, you need multiple servers for each of the RDS role services, but not all RDS role services automatically become highly available just because you add more servers running the role service. This principle also can be applied at other levels of infrastructure such as networking, network services, and data center power. For example, within a server, using mirroring (RAID 1) for disks ensures that that failure of a single hard disk does not cause the server to fail. To make infrastructure highly available, you need to make it redundant.
#WINDOWS SERVER 2012 RDS PER USER CAL OFFLINE#
There will be a service outage if that server has hardware problems or is taken offline for maintenance. For example, if you have only one RD Session Host server, that is a single point of failure. To achieve high availability for a service such as RDS, you need to identify single points of failure in the infrastructure and work to eliminate them. With 99.999 percent uptime, the allowed service downtime is reduced to only 5 minutes per year. For example, a requirement for 99.9 percent availability allows 8.75 hours of downtime per year, or approximately 40 minutes of downtime every four weeks. High availability often is expressed numerically as the percentage of time that a service is available. A highly available service is one that is available almost all of the time.
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