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Asked: 2026-05-17T21:02:29+00:00

I have a read only database (product) that recides on its own Sql Server

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I have a read only database (product) that recides on its own Sql Server 2008.

I already optimized queries by looking at most expensive queries in activity monitor – report. I ordered the report by CPU-cost. I now have something like 50 queries/second and no query is longer than 300ms.

CPU-Time is ok (30%) and Memory is only used by 20% (out of 64GB).

There is one issue: disk time is at steady 100% (I looked at idle time performance counter and used ideras SQL diagnostic manager). I can see that the product db behaves different than my order db which is on a different machine and has smaller tables: If I look at a profiler trace I have queries in product-db that show a value in column “read” higher than 50.000. In my order DB these values are never higher than 1000. The queries in product-db use a lot of Common table expressions, work on large tables (some are around 5 Million entries).

I am not shure if I should invest time in optimizing queries for i/o performance or if I should just add a server. By otimizing for query duration I already added the missing indexes. Is optimizing for i/o something that is usually done?

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1 Answer

  1. Editorial Team

    In short, yes. Optimize for both CPU and IO.

    Queries with high CPU tend to be doing unnecessary in-memory sorts, (sometimes inefficient) hash joins, or complex logic.

    Queries with high IO (Page Reads) tend to be doing full table scans or working in other inefficient ways.

    9 times out of 10, the same queries will be near the top of the list, but if you’ve worked on the high CPU and you still are unhappy with performance, then by all means, work on the high IO procs next.

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