February 24, 2009, 12:47 PM — For many companies, email has become a more important communication tool than the telephone. Internal employee communication, vendor and partner communication, email integration with business applications, collaboration using shared documents and schedules, and the ability to capture and archive key business interactions all contribute to the increasing reliance on email.
As a result, Exchange high availability has become increasingly important to businesses of all sizes. To help your company get started, Marathon has put together these five tips, which are easily-digestible pieces from our “Protecting Microsoft Exchange in Physical and Virtual Environments” white paper.
Step 1 – Protect Against Server Failures with Quality Hardware and Component Redundancy
Server core components include power supplies, fans, memory, CPUs and main logic boards. Purchasing robust, name brand servers, performing recommended preventative maintenance, and monitoring server errors for signs of future problems, can all help reduce the chances of Exchange downtime due to catastrophic server failure.
Downtime caused by server component failures can be significantly reduced by adding redundancy at the component level. Examples are: redundant power and cooling, ECC memory, with the ability to correct single-bit memory errors, and combining Ethernet cards with RAID.
Step 2 – Get Rid of Storage Failures with Storage Device Redundancy and RAID
Storage protection relies on device redundancy combined with RAID storage algorithms to protect data access and data integrity from hardware failures. There are distinct issues for both local disk storage and for shared, network storage. For local storage, it is quite easy to add extra disks configured with RAID protection. A second disk controller is also required if you want to protect against controller failures.
Access to shared storage relies on either a fibre channel or Ethernet storage network. To assure uninterrupted access to shared storage, these networks must be designed to eliminate all single points of failure. This requires redundancy of network paths, network switches, and network connections to each storage array.
Step 3 – Prevent Network Failures with Redundant Network Paths, Switches and Routers
The network infrastructure itself must be fault-tolerant, consisting of redundant network paths, switches, routers and other network elements. Server connections can also be duplicated to eliminate failovers caused by the failure of a single server or network component. Take care to ensure that the physical network hardware does not share common components. For example, dual-ported network cards share common hardware logic, and a single card failure can disable both ports. Full redundancy requires either two separate adapters or the combination of a built-in network port along with a separate network adapter.
Step 4 – Forget Site Failures with Data Replication to another Site
Site failures can range from an air conditioning failure or a leaking roof that affects a single building, a power failure that affects a limited local area, or a major hurricane that affects a large geographic area. Site disruptions can last anywhere from a few hours to days or even weeks.
There are two methods for dealing with site disasters. One method is to tightly couple redundant servers across high speed/low latency links, to provide zero data-loss and zero downtime. The other method is to loosely couple redundant servers over medium speed/higher latency/greater distance lines, to provide a disaster recovery (DR) capability where a remote server can be restarted with a copy of the application database, which only misses the last few updates. In the latter case, asynchronous data replication is used to keep a backup copy of the data.
Data replication is combined with error detection and failover tools to help get a disaster recovery site up and running in minutes or hours, rather than days.
Step 5 – Consider Virtualizing Exchange for Better High Availability
The latest server virtualization technologies, while not required for protecting Exchange, do offer some unique benefits that can make Exchange protection both easier and more effective. Virtualization makes it very easy to set up evaluation test and development environments without the need for additional, dedicated hardware. Virtualization also allows resources to be adjusted dynamically to accommodate growth or peak loads.
