10 September 2010
Friday
Understanding the relationship between WAN optimization and remote offices
By Allan Tan | Mar 23, 2009
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PrintThe amount of drive cache depends on the size of the appliance. A WAFS appliance intended for small offices may only use 100 GB with up to 2 Mbps of WAN connectivity. Appliances for larger offices may reach 750 GB with 10 Mbps of connectivity, and enterprise-class WAFS appliances may supply 3 TB with more than 300 Mbps of connectivity.
WAN optimization
WAN optimization is an important attribute of WAFS technology. The amount of optimization varies with the application. Some WAFS appliances provide TCP acceleration by repackaging the data into larger packets, which improves the WAN performance of a TCP application. The latency of specific applications can be further reduced by reducing the number of individual handshakes needed to transfer data. Storage administrators should understand the applications in the enterprise and consider the amount of acceleration that each application will achieve.
WAFS file limitations
WAFS still has limitations. One is that WAFS relies on caching to store key files locally. This means there may be several copies of a file located in the network. Not only can this compromise security by multiplying the exposure of a file, but it also makes it difficult to keep versions straight, as different users access files from different locations.
Furthermore, because WAFS does not support differential changes, file synchronization is not very efficient. When a file changes, even a small change, the entire file must be sent again. As a result, active files may demand significant bandwidth as they try to remain synchronized between locations. The way to mitigate these problems is to discuss these limitations with your WAFS vendor and establish best practices.
