In order to figure out if you need more memory for a SQL Server you can start by taking a look at Buffer cache hit ratio and Page life expectancy.

Buffer cache hit ratio

Here is what Books On Line has to say about Buffer cache hit ratio

Buffer cache hit ratio

Percentage of pages found in the buffer cache without having to read from disk. The ratio is the total number of cache hits divided by the total number of cache lookups over the last few thousand page accesses. After a long period of time, the ratio moves very little. Because reading from the cache is m...

Your testbed has to have the same volume of data as on production otherwise you are not really testing anything.

This blogpost is kind of a rant after I noticed this post on Stackoverflow

I do not believe there is a problem with the create trigger statement itself. The create trigger statement was successful and quick in a test environment, and the trigger works correctly when rows are inserted/updated to the table. Although when ...

Microsoft made available the Troubleshooting Performance Problems in SQL Server 2008 white paper on their site. This white paper is 102 pages long, the scope of this white paper is limited to the problems commonly seen by Microsoft Customer Service and Support (CSS).

Below is what is covered in this white paper:

Introduction

Goals

Methodology



Resource Bottlenecks

Tools for Resolving Resource Bottlenecks



CPU Bottlenecks

Memory Bottlenecks

I/O Bottlenecks

tempdb

Slow-Running Queries

Exten...

Adam Machanic created an item on connect explaining how LINQ to SQL queries involving strings cause SQL Server procedure cache bloat

If an application is using LINQ to SQL and the queries involve the use of strings that can be highly variable in length, the SQL Server procedure cache will become bloated with one version of the query for every possible string length. For example, consider the following very simple queries created against the Person.AddressTypes table in the AdventureWorks2008 database:

Dinesh wrote a blogpost about .NET Framework 3.5 SP1: LINQ perf improvements (LINQ to Objects and LINQ to SQL). There are three perf improvements in the just released SP1

Specialized enumerable: The new implementation recognizes queries that apply Where and/or Select to arrays or List<T>s and fold pipelines of multiple enumerable objects into single specialized enumerables. This produces substantial improvement in base ove...