Microsoft Sharepoint Products and Technologies Resource Kit eBook

Chapter 10: Performance Monitoring in Microsoft Office SharePoint Portal Server 2003 243
Leading Indicators for Index Servers
The key performance thresholds for index servers are 80 to 85 percent processor
time and 85 percent memory availability. However, the decision to add an index
server is more a function of indexing and propagation time than of monitoring performance
counters. When indexing and propagation cannot proceed fast enough to
keep content indexes as up to date as your customer’s business requirements
demand, you should add another index server. For example, if it takes two hours for
an incremental crawl and propagation when you need half-hour updates, consider
adding an index server.
Factors Influencing Index Server Performance
Depending on business requirements, it might be acceptable to have as many as
5 million documents in one content index, but if the rate of change is high and alerts
are popular, you might need two or three index servers for that data. Performance
of an index server also depends on the location of the crawled content and the processing
power of the index server. Crawl times depend on many factors, including
the following ones:
■ Content location and network performance. Content location and network
performance are related. For example, when crawling content outside of
your corporate LAN, performance might slow down. Crawling sites within your
intranet with adequate bandwidth is generally faster.
■ Type of documents in the index. You might be crawling sites that contain
a variety of document types, such as Microsoft Word, Excel, or Visio, in
addition to HTML files. Some file types are more resource intensive than
others.
■ Frequency and type of content index updates. The update schedule can
be as frequent as a weekly full update with an incremental crawl every 15 minutes
or something much less aggressive. You might be able to improve indexing
performance by adjusting your crawling schedule to crawl less frequently
if this can be done without affecting your ability to meet the business
requirements.
Scale-Out Limitations for Index Servers
If your existing architecture is a medium server farm, adding an index server
requires that you scale to a large server farm. This also requires the implementation
of two dedicated search servers, which is the minimum supported configuration for
a large server farm.
Microsoft recommends no more than four index servers per large server farm.