One of the frustrating realities about OST files is that they become progressively slower as they become older. One of the factors influencing this is fragmentation. You may argue that your defrag utility SHOULD do this for you, but how do you know for sure?

I'm going to use Contig.exe from Sysinternals to reveal all. I'm going to navigate to my Outlook application directory in my Vista profile and run

contig -a

to show me the number of fragments each ost file is in. I have several Outlook profiles and therefore several ost files.

You can see below that outlook4.ost is in 125 fragments!

The next step is to defrag all OST files. I'm going to do all of the ost files all at once in the current directory by running

contig *.ost.

The net effect after defragmentation is a maximum of 2 fragments in each file. Running

contig *.ost

again reveals that the files are as defragmented as contig.exe can with the following message :

"All files were either already defragmented or unable to be defragmented."

In summary, if your ost is running slow and you've looked at the other performance indicators that I've blogged about already, try defragging your OST file reguarly. If nothing else, you now know how to report on the level of fragmentation of your ost files.