We currently have an Exchange 2010 server on AWS. We want to migrate to Office 365, and have a free non-profit subscription. We are not ready to make the move yet to Office 365 but need a better backup solution (we currently only have AMI images on Amazon, which are costly, and are a temporary fix to a larger issue) then what was in-place from the old IT consulting firm. That being said is there anyway we can make a hybrid solution, where we simply use Office 365 as a backup for the On-Premise exchange server? We have setup a hybrid solution where users are on one or the other, but can they be technically "on both". Then when we are ready, all the data will already be there, and we can finish the migration quickly.

  • I don't think it will allow you to setup the migration like that. A cutover migration would allow something kind of like that, but you can't go that route obviously. But regardless, O365 doesn't perform a true backup, it just utilizes DAG. If your Exch2010 is on-prem why aren't you backing it up locally to disk or tape? – TheCleaner May 7 '14 at 20:24
  • Right now the Exchange 2010 server is on AWS. Our backup to disk would be an snapshot in AWS or S3. The people who setup the Exchange server did not setup backup correctly. We are temporarily storing it as an AMI until we come up with a better backup solution. Since the migration to Office 365 is inevitable but not currently possible, we figured it would be easier to just have Office 365 be a clone. Is it maybe possible to have Office 365 act as an exact clone of the Exchange 2010 server without routing mail to it? – David Eisen May 7 '14 at 20:31
  • Ah..then it isn't "on-premise" (at least for what most would read it as). But you said "hybrid deployment"...so let's be clear before I answer...are you currently setup on O365 in hybrid mode with some users there and some still on Exchange in AWS? How many mailboxes and how large are we talking? – TheCleaner May 7 '14 at 20:40
  • We do not currently have it setup at all. We are simply in the planning phases. We can easily do what you are describing, but have not done any actions yet. There are a little over 400 users in the organization, totaling 600gb. – David Eisen May 7 '14 at 20:44

DISCLAIMER: While the below "should" work...I'd be cautious about undertaking it as your "backup" solution, as that's not what it is designed for.

Because you haven't setup O365 at all, in theory you could do the following, assuming you plan on going to O365 within 60 days (I believe that's the limit):

  • Setup O365 for a cutover migration (you need to really understand what a cutover migration is, how it works, etc. before proceeding) but don't actually DO the cutover. Just the staging part. You'll setup the TXT record for the domain, and then setup the Exchange migration sync part.
  • Start the sync and just let it sync each day for each mailbox
  • DON'T, repeat DON'T finalize the cutover migration in the portal until you are fully ready to cutover...as once you do syncing will stop.

Note: this only handles mailboxes, not public folders or anything like that.

Basically what you'll be doing is a cutover migration but you'll be taking your time doing it. If all mailboxes sync within a few days, then at that point if your Exchange server on AWS fails, you could basically force the finalizing of the cutover quickly (MX records at this point, finish the cutover wizard, etc.) and retain all the email up to the last sync (happens every 24 hours or manually).

That's about the best I can think of.

  • Not optimal, but may work temporarily at least. – David Eisen May 7 '14 at 21:27
  • Possibly...just realize that with 400 users a hybrid deployment if possible would be an easier undertaking than a cutover migration. I also don't know for sure (but I believe you can) cancel a cutover migration in progress and then just delete the newly synced/created mailboxes on O365 to start from day 1 of your migration in the future. I'd really recommend contacting O365 support prior to starting down this path. Just setup the O365 account and open a ticket with them prior to moving forward. I'd be interested to hear what they say if you don't mind posting back. – TheCleaner May 7 '14 at 21:30
  • Hi, I have to find out if this is what the client is looking for. I appreciate all your help though. If the client does want to proceed I will keep this updated. – David Eisen May 7 '14 at 21:42

No. You cannot make an O365 instance be a "clone" of your own Exchange instance. A single mailbox can only be in one or the other.

You can also not stretch a DAG between your Exchange server and O365.

  • What about setting an eternal migration? It updates migrated mailboxes every 24 hours, but does it require they be active? – David Eisen May 7 '14 at 21:09
  • I don't know that you can complete a migration if you lost your source. Why don't you just add another DAG member in a different availability zone to your existing AWS exchange org? – mfinni May 7 '14 at 21:21
  • The main reason is due to the additional cost. At that point we might as well just backup to S3 and buy professional backup software, but we are getting rid of On-Premise so we have to do a ROI on that. – David Eisen May 7 '14 at 21:26

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