Exchange 2007 to 2016 Storage Sizing.

lamakama used Ask the Experts™
Hello All,

I had a question that hopefully you can answer. We are migrating from Exchange 2007 to Exchange 2016 (with a 2013 hop) and we are trying to properly configure the sizing on the server.

These new server for exchange 2016 will be on a ESXi/SAN environment.

Our current setup is:

500MB~ Average mailbox size for 450 mailboxes
100~ messages send/receive on each mailbox
8 Databases totaling only 480GB about 60GB each
3 servers. 2 mailbox, 1 cas.

Future setup:

Same as above except we will have a DAG protecting 4 databases.

Our PS team came back with needing almost 15TB of storage per server, 2 new servers. This seems excessive and something we do not currently have available on our SAN.

If you need any info please ask. Thanks.
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Scott CSenior Engineer
I agree...that seems excessive.

Here is the Exchange 2016 sizing calculator.

Run your numbers through that and see what it gives back.

With a total size of under 500 GB in databases, I'd say you'd be fine with 1 TB for each server.  Maybe 2 if you expect large growth.

I'm not sure what your PS team is thinking.



Not exactly sure what the results are telling me here. The two tabs don't add up to each other and the OS volume isn't there.


Exchange 2007 implemented single instanciation for attachments. Thus, if a user sent a 100 copies of a 1 Mb .PDF to other users on the same server, with Exchange 2007 this would occupy 1Mb, on  Exchange 2010 it would consume 100Mb.

Thus, you should expect the database on the Exchange 2010 server to be significantly larger than it was once you move the same mailboxes from Exchange 2007.  Of course, if you have users "clean up" before the move and delete unneeded emails, you may have a database with a lot of "white space", which will end up smaller on the new server.

How much moving away from single instanciation will increase storage need is difficult to determine, however anywhere from 10% to 100% (your 60Gb store files blowing out to between 66Gb and 120Gb) is typical.

This still does not explain the 15Tb requirement, 1Tb will probably be adequate. I would not specify less than about 2Tb.
E ATech Lead

Exchange 2016 requires essentially the same RAM/CPU/IOPs per mailbox as Exchange 2013 but requires just a little more compute requirements.

Exchange 2016 only has a single role (MBX role) so the Exchange 2013 guidance needs to be followed for multi role servers.

See here for more information on these changes:

Also check this article:

Hope this helps!
Scott CSenior Engineer

Sorry I didn't get back to you sooner on your results.  Yes, sometimes the numbers don't come out exact, but they do show that you don't need anywhere near 15 TB of storage.

Glad we could help.

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