Can .pst file be located in Onedrive?

Its not so much sync as that MS Outlook requires full read/write access to the pst, and the slightest network glych can lead to pst corruption (Network glych applies equally to a LAN connection)

All of my email accounts support IMAP so I just configured Outlook on my 3 different PC's with the IMAP account info. All the data is still on the mail servers so I'm not concerned about where those associated pst/ost files reside. All 3 PC's sync to the same data via the IMAP account.

However, I have a couple of archive PST files for my long-term data that is local to one PC. I wanted to have access to those 2 PST files from all three PC's. I copied the 2 PST files to my onedrive and it's been working fine from there on one computer, with those pst's connected to that PC's Outlook profile. When looking at OneDrive on a second PC, I can see one of the PST's that is 17MB, but not the other one (2.5GB). While I was excited at first of the prospect of having a single common set of archive pst's that I could move files into from my email accounts from any PC, and retrieve info from there as well, I sense a showstopping issue.

Even if I could get the 2.5GB pst to "sync" to all PC's and them connected to the Oulook profiles on all those devices, my laptop could be a problem. I believe that OneDrive is "object storage" rather than "block storage"? Every change to the PST file requires the entire 2.5GB to be written to OneDrive, even if I drop a 1K email message into a folder. If I'm traveling and using my iPhone as a broadband connection device, I'm going to waiting a long time for each "sync" and even worse, I'll be hitting my 10GB data package limit in a matter of minutes. These object storage systems are great for photos, music and other discrete files that don't change often, if ever, but they are not designed for "database" type of problems where you open a file and read/write into it, without re-writing the entire database file.

Am I correct in my understanding of how this will work? Thoughts and comments, please.  I think I'm on the wrong solution path for a shared PST archive.

The main issue is that OneDrive is a file synchronization program.  On the other had a PST file is a database.  Whenever the PST file changes then the ENTIRE file would have to be synchronized.  However this will happen only when the OS can detect if any update has been made to the file.  Moreover the file will remain open as long as Oulook has the file open, so unless OneDrive support VSS (Volume Shadow copy Service).  Even if OneDrive supported such a feature, it would have to have enough quiet time to make a copy of the file locally and then copy then entire file up.  This VSS support would have to be done on a periodic basis as there is no way to detect when the PST file has been updated while Outlook has it open.

The other issue would be synchronization between two devices.  As most PST file continue to grow, the OneDrive copy that is newer that another device must be downloaded on the other device before the user opens/uses Outlook.  If the PST file is large and/or the internet connection is slow etc.... what is to guarantee that the other device PST  file is not opened and updated before the OneDrive is synched?  And if this happens now what?  We have PST file on OneDrive that has information that the PST file on the other systems does not have.   What will OneDrive do?  Most likely I would think is to copy the file from the other system to OneDrive thereby loosing the information contained in the old version of the PST file on OneDrive.

Exchange on the other hand communicates programmatically with between the Outlook Client and the server.  In this way they determine what information needs to be synchronized.  Note that external local PST files will NOT be synchronized with the exchange server.  You would have to create a separate file on the server if allowed.

So in summary OneDrive will backup files that normally are not opened all the time such as databases.  As a result it is unusual that a file that is synchronized between two computers is updated independently at around the same time creating a potential collision for OneDrive.  This is not true of mail PST files.

If on the other hand Outlook uses the PST file directly from OneDrive, the issue is that the communication link is not consistent, and Outlook is not made/designed to use PST over links that are not necessarily persistent, and over high latency connections.  As a result a corruption of the PST file is not a case of if, but when it will be corrupted.

So in short unless Exchange is used to synchronize the PST file, some other solution needs to communicate programmatically with the Outlook client to provide a synchronized PST file.  Currently I don't know of such a program that would talk to Outlook Client to outlook Client synchronizing one or more PST files such that they are identical.  Outlook does not support multiple Outlook clients using the same PST file by the way.

I hope that this helps.

An excellent, cogent, and thoughtful response.  Not the answer I was hoping for, but clear and definitive.  Going to have to do more research on affordable exchange and exchange-like products.

GREAT thread here. Let's take this up a notch.... :-) . So first, some “cloud storage 101” basics….

I think this boils down basically to using a block storage versus object storage system, doesn't it? All of the free cloud storage systems, that general consumers are aware of, are "object storage" systems (Box, Dropbox, One Drive, Google Drive,...). When a change is made to the "object" the entire object (in this case a pst file) must be re-written, not just the part you change inside the file. Object storage is GREAT for storing things that don't change much if ever (photo's, music, etc).

Block storage on the other hand, provides fixed-sized raw storage capacity. Each storage volume can be treated as an independent disk drive and controlled by an external server operating system. This block device can be mounted by the guest operating system as if it were a physical disk and is usually pretty good for databases and things in which a file is “opened” and only part of it is modified when a change is made.

However, Amazon AWS offers a free tier of block storage in their S3 and EBS services (at least for a year?). S3 offers 5GB free and EBS offers 30GB free (you do need to provide a credit card to sign up). The only problem with block storage service is that you need to connect it to a virtual server within the cloud providers network which is not free (please correct me on this if someone is otherwise aware). The good news is that the storage is persistent and does not go away or get erased when it is not connected to a virtual server. I did price out the cheapest 24x7 virtual server at $0.015/hour, or basically $10.95 a month if you left it up and running non-stop. It would be significantly less than that if it was used a few hours a day, along with the storage. The service may start charging for the storage after year 1 as well.

So my question is, is it reasonably feasible to use an Amazon, Microsoft Azure, Google Compute block storage service to permanently load your PST files on, and use them remotely from multiple PC’s (albeit one at a time)? It still remains a discussion as to whether this would make sense cost-wise.