I have a medium Moss farm 3 frontend servers Index server and DB server. I am at the part of adding the index server to the farm all is good but I am confused on the 2 check boxes "Use this server to index content" and "User the server for serving search queries"
What is the difference? Do I check both if this is a dedicated Index Server?
This is a very important distinction, and the decisions depend on your preferred architecture and performance. The index portion is definitely a requirement for making that your dedicated index server. This gives it the role of building and storing the index. The query role does not have to be on your index server. You can instead use your web front ends (1 or more) as query servers. What this does is it tells the index server to propagate its index to the WFEs that are set as query servers so that they have a local copy of the index. Then, when someone does a search (this is done on the WFE), then that WFE will search itself locally instead of going across the network to query the index server. This increases speed at the time of query, but it of course introduces additional overhead in terms of having multiple full copies of the index on the network and the network demand of propagating those index copies all the time. If you select the query role on your index server, then the index will not get propagated and all searches will query the index server across the network. Oh, btw, to set WFEs as query servers, you have to activate the Office Search Service and only select the query checkbox, then tell it where to store the index.
One last piece of info to be aware is that there is also a crawling role that is defined in the SSP settings. The crawl server (or servers) is the WFE that the indexer uses for crawling content. A new concept being used (or at least new to me) is that you can actually make your index server a WFE that isn't part of your normal web browsing rotation (not load balanced) then set itself as the dedicated crawler. What this does is allows the indexer to crawl itself, which does two things: avoid the network traffic of building the index across the network and eliminates the crawling load on the WFEs. Since your index server becomes an out-of-rotation WFE for regular browsing, you can actually use it to host your Central Admin and SSP web apps, which again reduces load/overhead on the content WFEs. Consider that option as it is what I am using on a current project thanks to some input from a colleague.
What is the difference? Do I check both if this is a dedicated Index Server?
This is a very important distinction, and the decisions depend on your preferred architecture and performance. The index portion is definitely a requirement for making that your dedicated index server. This gives it the role of building and storing the index. The query role does not have to be on your index server. You can instead use your web front ends (1 or more) as query servers. What this does is it tells the index server to propagate its index to the WFEs that are set as query servers so that they have a local copy of the index. Then, when someone does a search (this is done on the WFE), then that WFE will search itself locally instead of going across the network to query the index server. This increases speed at the time of query, but it of course introduces additional overhead in terms of having multiple full copies of the index on the network and the network demand of propagating those index copies all the time. If you select the query role on your index server, then the index will not get propagated and all searches will query the index server across the network. Oh, btw, to set WFEs as query servers, you have to activate the Office Search Service and only select the query checkbox, then tell it where to store the index.
One last piece of info to be aware is that there is also a crawling role that is defined in the SSP settings. The crawl server (or servers) is the WFE that the indexer uses for crawling content. A new concept being used (or at least new to me) is that you can actually make your index server a WFE that isn't part of your normal web browsing rotation (not load balanced) then set itself as the dedicated crawler. What this does is allows the indexer to crawl itself, which does two things: avoid the network traffic of building the index across the network and eliminates the crawling load on the WFEs. Since your index server becomes an out-of-rotation WFE for regular browsing, you can actually use it to host your Central Admin and SSP web apps, which again reduces load/overhead on the content WFEs. Consider that option as it is what I am using on a current project thanks to some input from a colleague.
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