Why Browser is installed under 90shared directory rathar than 100Shared?

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After installing SQL Server 2008, some users might notice that sqlbrowser.exe is installed under %ProgramFiles%Microsoft SQL Server90Shared, rather than %ProgramFiles%Microsoft SQL Server100Shared as some users expect. When setup fails for some reason, some user may think this is the culprit. As matter of fact, this is by design, not a bug.

Some backgound here. SQL Server 2005 is also knowns as SQL Server 9 (code name Yukon), and SQL Server 2008 is also known as SQL Server 10 (code name Katmai).  So, usually shared component of SQL Server 2005 is installed under 90Shared and shared component of SQL Server 2008 is installed under 100Shared.

Then, why do we install sqlbrowser.exe under 90shared, rather than 100shared during SQL Server 2008 setup? The short answer is that SQL Server Browser is a shared component, not only by all instances of SQL Server, but also by different versions of SQL Server, i.e. It's shared by all SQL Server instances on a machine, no matter the instance comes from which version of SQL Server.

SQL Server Browser service used UDP port 1434 to receive request and send information about SQL Server instances to clients. Only one process can listen on that port. This basically means that there can be only one running SQL Server Browser service on a machine.

In order to support SQL Server 2005 and SQL Server 2008 Side-by-Side(SxS), the binaries (sqlbrowser.exe and its resource files) need to be kept in the same place. Otherwise, we have to uninstall SQL Server 2005 Browser before installing SQL Server 2008, but it is not feasible without some complicated redesign. More importantly, we need to support the case that customer install SQL Server 2005 after SQL Server 2008.

The installation of SQL Server Browser binaries are managed by Windows Installer. The SQL Browser component in SQL Server 2005 and SQL Server 2008 share the same GUID in term of Windows Installer. Windows installer will make sure the binaries on the box is always the newest one. The component will be ref-counted and will only be removed when the refcount decreased to 0.

SQL Serve Browser bacomes a seperate application starting from SQL Server 2005. In SQL Server 2000, Browser service is a thread in sqlservr.exe. So, users can consider Browser compoment was introduced in SQL Server 2005 and that's why it's installed under 90Shared.

For the similar reason, SQL Server Browser group is kept the same as SQLServer2005SQLBrowserUser$<MachineName> in SQL Server 2008. SQL Server resources (registry and file folders) are ACL'ed to this group and it's needed to keep the same in order to access the resources.

Xinwei Hong, SQL Server Protocols
Disclaimer: This posting is provided "AS IS" with no warranties, and confers no rights