Arthur Fuller is a well-known SQL guru and developer, but his system administration skills don’t reflect enough respect of his server. In this account of a bad SQL Server 2005 Express install he foo-bars his server by installing SQL Server 2005 Express on the same box that runs SQL Server 2000.

Database servers, the programs that provide the database functionality, don’t share resources well. These programs aren’t related to simple file-based Access or Borland databases. Those file-based programs are glorified text files and don’t require the resources that ACID compliant databases do. To be and ACID database requires real time access to server memory, logs files, and OS resources. By running two databases on the same system the most basic requests for resources from the OS can conflict, causing greater queueing and resource demands than splitting the instances to two equivalent servers, which drive up processor load and dramatically impact performance.

From experience, running both SQL Server and MySQL on the same development system, with no active users, does cause delays in both programs. That being said, multiple SQL Server versions on the same system definitely cause conflicts - something to remember if you’re going to demo MSSQL 2005 (virtualized OS’s via VMWare or Microsoft Virtualization Server are a different story, but if you’re smart enough to install enough RAM to support them then you can make up your own mind on running multiple SQL Servers).

Carry this one step further and try to keep Exchange, which uses its own databases, any other databases (Advantage, MySQL, Oracle, etc.), and any beta software on separate system and never have to recover from Mr. Fuller’s problem.

Update: “You can also install SQL Server 2005 side by side with SQL Server 2000 or SQL Server 7.0″ according to Microsoft MSDN. It “must” be OK if Microsoft says it will work, just remember that RAM use could double once that second instance starts allowing connections. (added 11/17/2005)

One Response to “Two Database Programs on One Server Equals Bad Idea (SQL Server Express 2005 Warning)”

1. Upgrading to SQL Server 2005 - New  by Mr. Tweak - Windows Network & Admin Tweaks, on November 20th, 2005 at 12:50 am, said:
   

   […] As I’ve griped about before: two databases on one server is a bad idea. Virtualization and watered-down heavy iron hardware make for exceptions to this, but it’s a setup to use tons of RAM and throttle specific OS systems if you run multiple instances on one server. […]

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