Why PST spells EVIL in a corporate environment

I’ve quite often seen in corporate environments the following scenario: The Microsoft Exchange servers have been under specified or outgrown their original requirements which results in disk constraints and ultimately outages. This in turn puts a strain on the IT department to resolve the issue, often without funds or time to do it properly.

So what’s the quick fix? Well someone will suggest “How about we get the client’s to use PST files?”. This can be combined in tandem with send and receive limits on the mailbox to force clients to use the PST. So the client has to archive to the PST file or they won’t be able to send or receive. The end result is the Exchange databases stop growing and stops the outages.

This probably sounds to good to be true, and it is. By implementing PST files another layer of complexity is added to the IT support structure and the initial benefits are quickly outweighed by the detrimental effects. The first issue is where the PST files are located. By default they are located on the local hard drive of the clients computer. If the client’s computer is replaced then the support technician needs to be aware that the PST needs to be retrieved or we end up with unhappy clients with missing mail messages. Additionally if a client uses multiple computers then we have a problem because the PST file contents will be different on every computer and once again we have unhappy clients. What happens if the PST file is corrupted or deleted? Well we restore it. Oh hang on, we don’t backup client computers so the mail messages are lost, and once again the client is unhappy. 

The solution that is often used for these conundrums is to store the PST on a network share. Not a bad solution? Well yes it is. What effectively has occurred is the problem we were encountering on the Exchange servers i.e. lack of disk space, has now effectively been transferred to the file servers. The disk space usage for file servers goes through the roof. The backup window for file servers increases even if the support team are doing incrementals. Why?, because just opening Outlook causes the PST file to be modified and therefore picked by an incremental backup. On top of all this Microsoft does not support opening pst files from network shares at all. In my opinion storing PST files on network shares is just asking for trouble.

So by implementing PST files the IT support team may temporarily alleviate the Microsoft Exchange issues but in the medium to long term they have just increased the support complexity. They’ve effectively fragmented the messaging system which was once a self contained entity, and often have simply transferred the problem onto the File Servers. 

So what are the options? Firstly and most importantly identify the problem before it becomes a problem. This can be achieved through various methods including enterprise monitoring systems, but even the smallest IT shops can at least use performance monitor to keep one step ahead of the curve. Once we know that trending indicates in 12 months time we are likely to encounter a problem, then a well thought out solution can be implemented and budgeted for. This could be a replacement program for the Servers or additional Servers to complement the existing, coupled with increases in SAN/Disk capacity, or potentially implementation of a third party archiving system such as EMC SourceOne or Symantec Enterprise Vault. It could even be as simple as limiting mailboxes to a certain size and forcing clients to delete mail.  

Even if you are caught out and are faced with needing a solution quickly, I ask you please do not slip into the trap and start using PST files.

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