Caches with the Write Stuff - Storage Technology Magazine
Do you think that collaborative file creation, editing, storage and management between geographically distributed users is a pipe dream? A new generation of startups doesn't think so. By combining traditional caching with techniques such as compression and two-way differential transfer, vendors DiskSites and Tacit Networks claim they can give remote users both read and write access to data over the WAN, at LAN-like speeds.

DiskSites' product, the W-NAS, consists of the DiskSites FilePort and the FileCache appliance. Posing as a CIFS/NFS file server, FilePort resides in the main office, and connects to the FileCache appliance in the remote office, managing caching and data transfer.

To cut down on the amount of data that travels over the wire, W-NAS transmits only those bytes that have actually changed. The result: Assuming a 128Kb/s connection with 100ms latency, and a 90% cache hit rate, DiskSites estimates that it can save a 600KB Word file in nine seconds--and 245 seconds without it.

Tacit Networks claims similar performance improvements using their Tacit Cache Server Appliances: Assuming 80ms latency, the simple task of recursively opening subfolders was clocked at 14 minutes, 48 seconds over the WAN, compared to 1.84 seconds over the native LAN. With a Tacit cache installed, WAN access time dropped to 1.91 seconds.

Tacit also claims a feature that its competition does not: coherent multi-site cache operation. Loosely translated, that means that means

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that multiple sites running multiple caches can simultaneously operate against the same complete data set.

To date, caching products have largely been used to distribute Web content, says Dan Tanner, analyst at the Aberdeen Group. Vendors selling caching products include NetApp and Cisco.

Meanwhile, geographically distributed users that might have benefited from real-time collaboration "have had to make do," Tanner says. Who are those users? Initially, Tacit is setting its sights on industries like engineering, publishing, financial and oil and gas, to name a few. Further on down the road, WAN consolidation technologies might address generic problems like remote backup.

This was first published in February 2003