I'm currently exploring the possibility of using Google Drive to automate backup of local files as I am already a paying customer with lots of free storage. I'm currently using Google Apps Email and would like to have my own backup of the service. I've found online web apps like Backupify and so on but wondering if I could use the Google Drive to backup my local .pst outlook file.

All sounds good until I'm greeted with the actual file size of the outlook PST file. It is 15gb and modified dozens to hundreds on a daily basis.

My upload speed is only 1mbit and I'm aware that 15gb would take a long time but would it need to upload the entire file again to Google Drive everything the file is modified or is it much more intelligent than that and only uploads whats changed?

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  • 1
    Wait...so you're using Outlook to back up Google Apps Email, then you're using Google Apps/Google Drive as the backup target for your PST file? – rob Mar 8 '15 at 6:15
  • yea, there it is a good example of recursion. – mtk Mar 10 '15 at 7:43

If you'd like to consider alternatives, Dropbox supports differential file sync on their desktop and web clients. Alternatively, if you are so inclined, you could achieve this yourself by using xdelta.

xdelta creates binary diff files. You could upload the huge PST file to Google Drive and keep a copy of the version that you uploaded somewhere safe on your computer or backup disk.

Now whenever you feel like syncing the changes made to the PST file (say once every 24 hours) you create a delta file by running this command (assuming you use a Windows system):

xdelta -e -s %PATH_TO_BACKUP_PST_FILE% %PATH_TO_MODIFIED_PST_FILE% > deltafile.delta

A new file named deltafile.delta will be created that contains just the modifications made to the original 15 GB file. The delta file will hopefully be small enough to be uploaded easily. However, if encryption is enabled, the delta file sizes might end up being larger.

You can automate this process by using batch files and the Task Scheduler or just run it manually.

To re-create the modified file from the delta file and backup PST file, run this command:

xdelta -d -s %PATH_TO_BACKUP_PST_FILE% deltafile.delta > modified-file.pst

As of 2012, Google Drive apparently still did not support differential file sync. If that's still the case, Google would sync the entire 15 GB file every time it changes.

It sounds like you're using Outlook to back up your Google Apps Email, then you want to back up the Outlook PST file to Google Drive. You may want to take a step back and consider what you are trying to achieve.

For example:

  1. Do you want access to your old email in the event that Google has a massive outage? If so, then syncing the PST file to Google Drive doesn't necessarily help in that scenario.
  2. Are you trying to protect yourself in the event that your Google account is compromised? In that case, the PST file stored in the cloud would be worthless because someone may have tampered with it.

Using Google Drive to store your PST-file backup of Google Apps Email only seems reasonable to me if Google Drive is syncing the PST file to at least one other device that you own. But in that case, you could use some other backup system like CrashPlan, which lets you use your own machines as backup targets for free.

But let's suppose that either the email in your PST file is for a different email account than Google Apps Email, or you have a great reason for backing up Google Apps Email to Outlook PST, then uploading the PST file back to Google (Drive).

One solution to your file syncing problem is built into Outlook. If you turn on AutoArchive, your old emails will periodically be "aged out" into a separate PST file. This will allow you to shrink the main PST file enough that it can be synced in a reasonably small amount of time, while the larger archive PST file--which is only modified during an AutoArchive operation--will be synced much less frequently.

Another solution is to manually create a new PST file every once in a while and move all your old messages to that PST file (for example, at the beginning of each year). Assuming the PST files are purely for archival purposes, you could then unmount the new PST file so Outlook will make no future modifications, compact your main PST file, and let the main PST file accumulate mail for another year. This may not be quite as convenient as the first solution, but it will still be better than trying to sync a 15 GB file several times a day. As a nice side effect, it also decreases the chances that your entire email backup may be lost in the event that a single very large PST file is somehow massively corrupted.


I understand you are using Outlook as a backup device for Gmail, which involves storing the emails in one humongous PST file.

I do not see this solution as being very efficient, and suggest using some other archiving mechanism.

I found some commercial products which might serve :

SysTools Gmail Backup

I have no experience with these products and cannot vouch for any of them. It is also unclear from their documentation whether the backups can be stored on Google Drive.

You can also use the free IFTTT website : "If This Then That". With it you may be able to define triggers that will store new Gmail mail on Google Drive. Examples can be found on the Connect Gmail to Google Drive page.

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