Outlook 2010, will multiple PSTs cause problems

Question

At the company where I work, the owners use POP/SMTP in Outlook to be able to keep an active multi-year history of emailed conversations. This history cannot be archived by date so they have been creating subfolders in their inboxes and filing the incoming mail into the folder corresponding to the sender's company.

They say they must have ALL this mail immediately at hand and easily findable no matter how old it is. This can mean 6 or 7 years of email. They constantly have corruptions in their PST and will not remember to run "scanpst" or any other re-organizing tools.

In an effort to solve the problem, I tried creating a second PST called "History" and letting them file their client subfolders in it by using "Move". This resulted in a 1-2 GB Outlook.PST and a huge History.PST which is never used for anything but storage.

It works so well I am afraid it is too good to be true and wondered if anyone else had ever tried this. Their Outlook now boots in a fraction of the time it did take and they no longer have corrupted PST's since the main Outlook.PST is never that large. The History.PST continues to grow (now over 12 GB), but does not appear to cause any problems or slow down Outlook in any way.
I figured if anyone anywhere else had ever done this, they could surely be found here. I offered the normal "archiving" option but was told they don't file by "date' and there is no given criteria I could use for automatically doing this.

If anyone can offer any suggestions or warnings about doing it this way, I would appreciate it.

Answer 1

The PST format works using a an efficient B-Tree structure, which allows it to grow to very large sizes without impacting performance too much. They're limited to a max of 50GB in size (http://support.microsoft.com/kb/832925) but I wouldn't recommend allowing them to grow that large.

Your main issue is going to be backing up those large files. Since the PST file is a single opaque data file every time it changes your backup solution will need to re-backup large parts of the data (or all of it if it's not very clever). A single added email can make very large changes to the file if there's an internal re-balancing of the B-Trees and data allocations.

Depending on how your users are using the History PSTs it might be worthwhile having multiple History PSTs based on age, e.g. 2005-2008, to reduce the modifications on the older files. I have users regularily working with >5 PSTs without any problems.

One final thing. If you're storing your PSTs on a network store you should read this: http://blogs.technet.com/b/askperf/archive/2007/01/21/network-stored-pst-files-don-t-do-it.aspx