<div>
Microsoft recommends a conservative 5 – 7 GB per hour for a defrag operation, which means that your server could be offline for up to 20 hours. &nbsp;That said, I know of one 45 gig db that took around 3 hours to defrag so it could be a lot less time - it really depends on how much whitespace is in your database and the hardware you are running on.<br />
<br />
You can run ESEUTIL with the /p switch to configure ESEUTIL to create the new defragmented database on an alternate location (for example, to a location on a different hard disk). This switch lets you preserve your original defragmented database (which lets you revert back to your original database if necessary). This switch also significantly reduces the amount of time it takes to defragment a database, because you are rebuilding to a new location, rather then rebuilding the database in place.
</div>


<div>
<blockquote>
You can run ESEUTIL with the /p switch to configure ESEUTIL 
</blockquote>
<br />
Michael Dyer, I think you mean <b>ESEUTIL /D</b> to do a defragmentation not <b>ESEUTIL /P</b> (a database repair switch). You only want to run /P as a last resort to repairing a corrupted database.
</div>


<div>
My understanding is that /D defrags in place, /P is necessary to defrag to a new location. &nbsp;<br />
<br />
<a href="https://support.microsoft.com/en-us/kb/192185" rel="ugc nofollow">https://support.microsoft.com/en-us/kb/192185</a>
</div>


<div>
Yes you are correct but the /P is used in conjunction with the /D in this case as in:<br />
<br />
ESEUTIL /D databasename /P<br />
<br />
But if you simply run ESEUTIL /P you are performing what is called a hard repair on the database.<br />
<br />
<a href="https://technet.microsoft.com/en-ca/library/aa997215(v=exchg.65).aspx" rel="ugc">https://technet.microsoft.com/en-ca/library/aa997215(v=exchg.65).aspx</a>
</div>


<div>
<div class="content wysiwyg-content">
Our databases are growing very fast. And after deleting lots of emails, of course, Exchange doesn't free up the white space. To do so we have to either create a new database and migrate users to it, then delete the old d/b OR use the offline defrag utility... eseutil.exe /D path\to\file.edb.<br />
<br />
My first choice would be the create a new database and migrate. That way the org mail is not down. But if we were to decide to go the offline defrag route, how can we get a general idea of how long it would take? We have five database each approximately 100Gbs on high availability virtual HDDs on ESX VMs with 12GBs RAM. I'd hate to tell my boss it could take 6-12 hours and it take 3 days...LOL.
</div>
</div>


Our databases are growing very fast. And after deleting lots of emails, of course, Exchange doesn't free up the white space. To do so we have to either create a new database and migrate users to it, then delete the old d/b OR use the offline defrag utility... eseutil.exe /D path\to\file.edb.

My first choice would be the create a new database and migrate. That way the org mail is not down. But if we were to decide to go the offline defrag route, how can we get a general idea of how long it would take? We have five database each approximately 100Gbs on high availability virtual HDDs on ESX VMs with 12GBs RAM. I'd hate to tell my boss it could take 6-12 hours and it take 3 days...LOL.

How to estimate the time required to offline defrag.

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.