PST = Personal Storage File. This is a file created by the user to store mail to 'locally'. That is, not on the server. If you aren't using Exchange, then all of your mail in Outlook goes into a PST. If you are using Exchange, you move your mail there when you hit your quota.
OST = Offline Storage. This enables 'Cached Mode' - aka, the ability to view your mail that is on the server without having connectivity to the server. Both files exist off the server. I won't say they reside on the local machine because you can choose to put them where you wish. By default, they live in %USERPROFILE%\Local Settings\Application Data\Microsoft\Outlook. Not that PSTs exist by default. If you want mail that you've moved to a PST (note the word move and not copy) then you'll need to back it up. The OST for all intents and purposes is disposable as it is meant to be an offline copy of the server's information. They do hold the mail in its entirety, including attachments. -- This is all information I've picked up and discerned from using and supporting the product and is as I understand it now. -- -----Original Message----- From: Matthew W. Ross [mailto:[email protected]] Sent: Wednesday, October 21, 2009 5:44 PM To: NT System Admin Issues Subject: Re: Outlook 2007, constant hard disk thrashing. Okay, I've been trying to following this, and as I know nothing of Exchange/Outlook... perhaps I misunderstood something... Help me clear this up: These PST/OST files, they are located on the Client, or on the Server? Because a 5TB partition just for a database on the server doesn't sound so bad. But each client with a spare partition for a Mail client's database file... that sounds ridiculous. And maybe that's where I'm mistaken... am I? If they're on the client, what does it hold? A copy of all the email including attachments? Does it need to be backed up? --Matt Ross Ephrata School District ----- Original Message ----- From: Ben Scott [mailto:[email protected]] To: NT System Admin Issues [mailto:[email protected]] Sent: Wed, 21 Oct 2009 11:25:30 -0700 Subject: Re: Outlook 2007, constant hard disk thrashing. > On Wed, Oct 21, 2009 at 2:10 PM, Phillip Partipilo <[email protected]> wrote: > > Sure my PST file is about 5 gigs, but 2003 never did this. > > FWIW, we've found that for large PST/OST files, putting them on a > dedicated hard disk partition helps Outlook 2003 performance > significantly. When mixed in with everything else, they fragment like > crazy and performance goes to hell. (And FYI, the Microsoft defrag > utility apparently can't handle files > 2 GB.) > > -- Ben > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ > ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
