Wide-Area File Services for Windows

Despite continual improvement in storage technologies, dealing with storage and remote sites remains a thorn in the side of many administrators. Concerns about cost, security, excessive exposure of proprietary business data, and overall maintenance (backup and management) of offsite data are problems that have yet to find broadly accepted solutions.

In high-latency situations, most applications--and particularly Windows-based applications--deal poorly with storage. Typically, applications expect a latency that's no worse than the latency that's characteristic of a LAN. When faced with the long latencies often encountered in WAN environments, many applications appear to hang or simply time out while doing large data transfers. The nature of the Common Internet File System (CIFS) means that even something as simple as saving a file, although it looks like a single action to the user, actually requires a conversation between the application and the storage location. Files must be divided into packets for transmission, and the application and the storage system need to exchange messages to acknowledge and verify that packets are being transmitted and the file is being saved.

This ongoing traffic is what makes Windows applications perform poorly over WAN connections. Consequently, most Windows shops make sure that local copies of business data are available to remote or branch offices so that user traffic doesn't have to go out over the WAN. Those organizations then just back up or update the remote server that houses the copy of the corporate data. However, this approach makes it difficult to propagate changes to the data in real time, and remote users are always a little behind the curve either in acquiring the latest corporate data or in updating the main-office database. Maintaining multiple copies of data is the antithesis of the portal approach that Microsoft advocates with Windows SharePoint Services and Microsoft SharePoint Portal Server 2003 and their integration with Microsoft Office, yet Office is among the applications whose performance deteriorates the most when they're forced to deal with excessive storage latency.

The goal of wide-area file services is to give remote offices LAN-speed access to corporate data without requiring copies of data or the additional management that they necessitate. Often based on some form of DFS, wide-area file services are in the early stages of development and adoption, with few proven viable solutions in the market--and until recently, no product for use with Windows Server.

But earlier this month, Tacit Networks (see URL below) announced that its cutting-edge wide-area file services solution would support Windows Storage Server 2003. Tacit's iShared appliance lets storage managers deploy one device at each remote location to give the users at that site data-access performance similar to the performance that main-office LAN users enjoy.

In addition to being simpler than installing dedicated servers at each remote location, the appliance approach gives corporations a solution that can be centrally managed, provides everything from flow control to file compression, improves the experience of remote users, and increases the efficiency of existing WAN links. In scenarios in which data needs to be refreshed regularly at each office, the appliances can be prepopulated (i.e., necessary data can be pushed to the appliance before remote users request it), further cutting down on WAN traffic. And all data is managed as if it resides only on the home office network--users don't need to be aware of what the appliance is doing.

Tacit built its technology in the Linux environment, and the iShared appliance is the first product to transparently support wide-area file services for both Linux and Windows Storage Server 2003 users. If you're responsible for dealing with remote or branch offices, you need to understand wide-area file services, because you'll most likely come to use them. Taking a look at the technologies that Tacit's iShared product uses is a good place to start.

http://www.tacitnetworks.com