Tacit Networks is upgrading its WAN optimization gear to perform better for companies that want to support wide-area file services to data centers.

Tacit's I-Shared devices sit at either end of wide-area connections, streamlining transfer of data and caching files to reduce the number of times information has to cross the WAN from remote offices. As businesses consolidate server farms to save on hardware and maintenance costs, WAFS is becoming more important so end users at remote sites don't suffer intolerable delays because of constraints of WAN connections.

One upgrade Tacit has in the works will improve local caching so that if the WAN link goes down, remote users can access files that have already been cached on their end.

Through the cache, customers also will be able to modify them and create new files. When the downed links come back up, I-Shared boxes will re-synchronize the files with the server where the files permanently reside.

The I-Shared devices can store 100G to 700G bytes of data, depending on the model. When the disks fill up, the devices purge those least used.

This upcoming feature is of interest to the World Bank Group because it would help keep staff working during what would otherwise be downtime, says Nasir Alizadeh, principal information officer at the bank. Even without the upgraded caching, performance on a T-1 link between Washington, D.C., and Chennai, India, improved with a Tacit box on either end, at least cutting transfer times in half, he says. In some cases, transfer times dropped from hours to minutes, he says.

Caching available on the Tacit gear now requires "lots of administration work" to let local users access the cache and to re-sync later, Alizadeh says. Connecting the offices is important enough that many of the bank's 107 sites have redundant WAN links to improve uptime, he says.

This Disconnected Operations mode also resolves any conflicts that might arise during an outage. For example, if users at different sites create new files with the same name while they are disconnected from the server, the Tacit gear will recognize the problem and store them under different names, the company says.

Tacit says it also will accelerate TCP between its boxes. The upgrade will improve performance of TCP traffic by making the protocol restart faster after packet loss or congestion throttles it back.