Exchange 2010 Documentation- Exchange 2010 Mailbox Server Role Design Example

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David Ayodele


I am reading a portion of the Exchange 2010 documentation-specifically the Exchange 2010 Mailbox Server Role Design Example (see URL) below
A part of the paragraph immediately after the "Example values for determining actual mailbox size on disk" table, states:
"...In this environment, each user will consume 2.25 GB of disk space. This solution will also leverage 1TB disks in a JBOD configuration; therefore the maximum database size is 667 GB....."
I just need some help in understanding how "the maximum database size is 667GB" came about(was derived) within the context of the example!



You have to take a holistic approach to this to really understand why it landed on 667GB. So, you start with mailbox size quota and user count. In this case we have 24,000 users and a 2GB quota from each user. You then calculate IO requirments for those users (the E2010 Mailbox storage calculator is the tool of your dreams for all of this by the way, just in case you didn't know about it). You then calculate how many mailbox servers you need to support 24,000 users using all this informaiton, with the understanding that using 1 x 1tb 7.2K SATA hard drive will host each log/database pair. SOO..with all that being said:

6 mailbox servers equals 102 active databases (16 databases per server) and 204 passive copies per server (DAG allows 16 copies of a database) which brings us to a total of 306 databases. We don't really care about that though, lets focus on the active number of databases.

24,000 users divided by 102 active databases = 235 mailboxes per database. <--I think this is the part you were missing

235 Mailboxes @ 2 GB's per mailbox (2GB is what you want to be your max mailbox size, not a hard limit, you decide) + whitespace + dumpster + 20% growth factor equals 635 GB's per database.

Transaction log generation based on message profiling indicates that for each database there will be 5.6 GB of tlogs per day, give yourself 3 days of growth (23GB) + content indexing (63 GB) and wallah.

635 + 23 + 63 = 900 GB approximatly. The last step is to verify that the disk itself can handle your IOPS requirments, and in this case it falls well within acceptable range.

I know, more than you asked for. Anyways, the 667 GB number is based off of the maximum allowed number of active databases (102), which divides into the maximum number of mailboxes (24,000), and of course the maximium mailbox size (2GB). Thats how it arrives.

I hope I made that clearer instead of more messed up.


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well i don't understand how you do your calcul michel de rooij :

is it something like this :

total size of the disk= size of the database +growhtfactor on the size of the disk + content indexing

which then provide this calcul :

total size of the disk - growhtfactor on the size of the disk =1,1 size of the database as

the content indexing is supposed to be 10/100 of the size of the database


i don't understand either how triton deep find the number of databases : if some of you can help me clear my mind on this stuff I would really appreciate.

David Ayodele

Hi Everyone,
Your contributions have been most helpful. I now have a better understanding of this design example ! and here is my own little piece:

Each user is said will consume 2.25GB of on disk space

Now we all understand how we arrive at 667GB out of the 1TB disk space [1TB Less (30% = 20% Free Space % Requirement + 10% Content Indexing) ]

So the 667 GB is the on disk space that will be available to host the Database

Now there is another Factor to consider and that is; the Database Growth Overhead = 20 % (From the Exchange 2010 Help Documentation - Read about "Database Growth Overhead")

In other words the database is expected to grow by 20%. So to plan for the growth reduce 667GB by 20% = 533.6 GB

To get the number of Mail boxes per database = 533.6 GB/2.25GB = 237.2 , Actually the First table in the example reads (2.25 +12%) but i cant really place the 12%, so i assume this ought to read (2.25 + 1.2%) = 2.277GB, the 1.2% is the factor from Single Item Recovery feature.

This then translates to 533.6GB/2.277GB = 234.3 , which if rounded up = 235 Mailbox Users

Now Each server is expected to accommodate 4000 users (4000 X 6 Servers = 24000 Users)

Number of Active DBs per Server = 4000/235 = 17.02

Total Active DBs for 6 Servers = 17.02 x 6 = 102 (In rounded Figure)

And of course the Passive DBs (Additional 2 Copies per DB) = 102 X 2 = 204

Total Number of DB copies = 102 + 204 = 306

I hope this is RIGHT. And if is i hope it helps someone


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