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Directory caching for speed

By Dave Kearns
Network World Directories Newsletter, 04/18/01

A couple of weeks ago I saw a press release that intrigued me, announcing a "directory caching server." I found it hard to fathom from the marketing-speak exactly how such a beast might work, since most caching servers/devices don't discriminate among the packets they see and serve. Nevertheless, I was intrigued enough to take a closer look.

What I found was a start-up called Ipedo, founded by former Critical Path Vice President Nick Zhang and currently headed by former RSA Marketing Director Tim Mathews. After checking out its product and talking to Tim and Nick, I think they just might be on to something - especially with Directory Services Markup Language (DSML) coming soon.

Nick's real expertise is with Java and XML, so it's no surprise that the directory caching product (called, with remarkable subtlety, "Ipedo Directory Cache") owes a lot to both Java and XML. And on the horizon is something called the XML Database Server, which promises to speed up XML (and, by extension, DSML) processing just as the directory cache speeds up directory access.

The downside of the cache server is that you'll need to add a new server in front of your directory, as well as use Ipedo's own directory as a front end to the Lightweight Directory Access Protocol-enabled directory you've already chosen. But if you don't already have a directory, Ipedo's will do everything you need.

The company's secret is the design of the Ipedo directory database in RAM on the cache server. You can load the entire directory - one or more partitions of the directory, or simply the indices - into RAM. By designing the database to run in main memory, Ipedo can deliver up to 10 times the performance of a disk-based directory (and it has the DirectoryMark numbers to prove it).

The only drawback I found was that the current version doesn't support journaling of writes, and the possibility exists that a server crash could wipe out changes. But the write-thru time is adjustable, and Zhang assures me that journaling and rollback will be part of the next version.

Ipedo is almost ready to announce its first customers - names you will recognize. If performance is the most important part of your directory strategy, then you owe it to yourself to investigate Ipedo's offering.