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What IIS the Limit?

Members of the ISP-Webhosting list discuss how many domains can be placed on a single Microsoft IIS server.

[November 1, 2000]

On the ISP-Webhosting list in October, KM queried,

"Is there a limit on how many virtual domains IIS [definition] can handle? I have had several people tell me that IIS doesn't do well with more than a few hundred virtual servers: is this true?"

JM suggested that there are a number of factors involved:

"I've heard similar things said regarding IIS. This has more to do with how IIS stores and manages the configuration information for all those sites than with the associated traffic. Since IIS can get pretty complex in its configurations of virtual web sites (with virtual directories, virtual applications, application extension mappings, permissions, etc.) it can put a pretty large strain on resources when a single server has to serve many hundreds or thousands of domains. I'm sure the limit varies widely with the complexity of the sites, and with the hardware configuration of the particular server."

The variety of responses backed up JM's explanation:

[GS complained] "We cannot run more than 250 domains ever on any machine with 256MB RAM."

[MS explained] "It depends on what you are running. IIS 4.0 and 5.0 can handle many hundreds of domains (we have one server with 800 domains on it) but it's generally not a good idea to have more than 400 or 500 per IIS server."

[MF offered] "IIS can very easily (with the proper hardware and tuning) handle as many as 1000 virtual domains. I've run this configuration with success; although it may not handle very heavy load, it'll have no problem if it serves straight HTML (nothing fancy). I've found that between 500 and 750 sites works great."

[BP boasted] "I've got 1800 virtual domains on a machine with 500MB RAM and it runs fine."

—End