Wide Area File Services (WAFS) refer to technologies that enable the consolidation of file servers from remote sites to the data center without compromising end user performance. From its initial launch, Riverbed's WAN optimization solution has delivered WAFS value to its customers. But by providing a WAN optimization solution, Riverbed has enabled its customers to do much more than a WAFS-only solution can do, by delivering application acceleration for all key enterprise applications running over TCP. While WAFS can be a useful tool for many users, it is only a part of the total remote office solution that most enterprises are seeking.

WAN optimization is a superset of WAFS. WAN optimization provides the benefits of WAFS while also addressing other key issues prevalent in enterprise WANs.

While WAFS solutions address bandwidth and application performance problems associated with file sharing, the typical enterprise has a heterogeneous mix of data and applications moving across its network to remote sites. The types of data include email, web-based enterprise applications, database applications, ERP, FTP, backup and replication, proprietary applications, and more. WAN optimization solutions, in contrast, accelerate all of these types of data transfers and applications. By using this acceleration approach, WAN optimization solutions solve the problems that WAFS address, but at the same time meet a much wider range of customer needs. In fact, several industry analysts have compared WAFS versus WAN optimization, and have determined that WAFS is just a subset of WAN optimization.

WAFS appliances - a type of caching appliance - work by storing copies of files that have been accessed over a WAN in local devices, so that subsequent users get accelerated performance. A WAFS-only solution however has serious limitations. The table below offers a comparison of some of the more important differences between a WAFS-only approach, and Riverbed's solution.

	WAFS Appliances	Steelhead Appliances
Applications Supported	File Systems	All TCP traffic
	Limited Email Support
Mechanisms	Cache copies of files	Application-independent data store
	Some support for email attachments	Application-specific latency optimizations
		Multiple TCP optimizations
Bandwidth Optimization	Only when cached files are requested	All TCP Traffic – typical reduction in overall WAN traffic is 60-95%
	Some support for email caching
Support for Disconnected Operation	Yes	Yes
Proxy for File Server	Yes	No
Transparent to Clients and Servers	No	Yes

Wide area file services can serve an important function for organizations looking to accelerate consolidated file servers. But WAFS comes with a number of limitations that are essential for every organization to understand:

• WAFS is limited to file sharing. WAFS products can only cache files that are sent over the WAN via application protocols they know, which means that they are limited primarily to CIFS and NFS caching.
• WAFS cannot deal efficiently with some changes to data. In the event of a change of file name or a move of a file from one directory to another, WAFS products typically require the complete file to once again be transferred across the WAN. This severely limits application performance optimization under many common use cases.
• WAFS keeps multiple file copies. The way WAFS operates, it must store many copies of a particular file throughout the network inorder to accelerate performance. Not only is this a security risk, but it can lead to versioning problems whereby users in different locations are accessing the different version of the same file.
• WAFS is not designed for disaster recovery. Because WAFS functions by short-circuiting the typical communications processes of applications, it does not help in disaster recovery scenarios. It also lacks any meaningful application protocol optimization in order to accelerate the performance of disaster recovery applications.
• WAFS may not ease IT management. WAFS is generally designed on top of windows servers. Instead of creating a true appliance design, WAFS appliances require IT managers to put the same amount of effort into managing WAFS servers as they would any other remote server.

For more technical detail on WAFS and its approach to application acceleration, download the whitepaper The Five Ugly Truths About WAFS and Caching.

Compared to WAFS-only products, WDS appliances offer a far broader solution that not only optimizes file sharing traffic and enables file server consolidation, but also provides the following important benefits:

WDS Key Benefits

• WDS accelerates the performance of all TCP applications on your WAN, including web applications, FTP, Exchange, web content (both static and dynamic), Lotus Notes, SMS, backup traffic, block and file level replication, and ERP applications. Acceleration of applications varies, but they can often be sped up by five to 50 times and in some cases up to 100 times
• WDS enables consolidation of a wide range of IT infrastructure: File servers, Microsoft Exchange servers, Lotus Notes servers, tape backup systems, and storage.
• WDS optimizes WAN bandwidth utilization, typically reducing usage by 60% to 95%.

In comparative evaluations of WAFS versus WDS, customers consistently select a WDS solution because it provides all the benefits of WAFS plus much more.