Exchange 2013 Available Database Capacity < Total Quota Limits

ejscn
ejscn used Ask the Experts™
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Is it possible to create mailbox databases in Exchange 2013 that are less than the total quota limits of the mailboxes within?

Here is the situation:  we are a smaller organization about to upgrade from E2007 to E2013.  Our current mailbox database (we only have one) is 144GB.  Because of this, our storage capacity on our new Exchange server is over 800GB, which we thought would be more than enough.  However, we offer 2GB storage quotas, and have 556 mailboxes, so the Exchange Server Role Requirements Calculator is spitting out a requirements of over 1.1TB for database storage alone, and that is after decreasing the quota on most of the mailboxes to just 1GB.

I realize we did this backwards, and I would like to not to replace a bunch of drives on a brand new server.  Because we know that most mailboxes won't ever use 2GB storage (the average mailbox size is < 250MB), is it possible to have mailbox databases that technically don't have enough storage for everyone to fill their quota?  Would it be a huge mistake to go that route, even if it is technically feasible?

Thanks in advance for your help.
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Most Valuable Expert 2014
Commented:
Exchange doesn't care what the quota is or even look at the number of mailboxes. It will have no impact on the configuration of the server. The calculator is just that, and it works on the worst case scenario which is everyone using the maximum of their allowed quota, hence the storage required. In reality, you will not have all users using all of the space allowed.

Simon.
hecgomrecNetwork Administrator
Commented:
I agree with Simon, the calculator multiplies the amount of mailboxes by the quota and that's why you get 1.2 TB of hard drive.


Now, you mentioned 1 Database and 556 mailboxes.  Please consider to spread out your mailboxes into more databases.  In case of failure it will be easy for you to recover the missing info and having databases to group departments, branches, etc. helps to speed up maintenance.

Imagine having everything in one hard drive that fails... the whole organization will suffer but if you split the databases and even put them in different hard drives only those on the affected drive will be affected the rest will continue working.

Also, if you keep too many logs files the amount of space increases.
ejscnIT

Author

Commented:
Thank you both for your help.  

Hecgomrec,  Our new server has 6 drives in a RAID 10 array that we were planning on partitioning into 10 drives - one for each database and log file.  We were only planning on using 4 databases and having a spare partition in case it's needed.  Would it be better to have separate physical discs for each database and log file?
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hecgomrecNetwork Administrator

Commented:
Planning... Planning!!!!


I personally have never created such a logical partition. I will create 3 RAIDs and 1 partition per logical drive.  In case of hardware failure (dead HD) it is pointless to have more than 1 partition they will be all affected.

I usually don't put more stress on the HD other than necessary, too many logical divisions on a virtual arrangement can open a door for failure and reduce performance.

Also, think about the following:  You had everything in 1 database before, how were you prepared for disaster?.  Will you better prepared this time just by having 3 HD and more databases to split the mailboxes?.

Again, every scenario is different and the way each IT person decide how to handle performance, functionality and recovery is also different.

My recommendation, base your decision on desire hard disk performance and fault tolerance you can afford and how much you trust and your backup plan.
ejscnIT

Author

Commented:
Thank you.  And agreed on the planning.  This is my first time moving to a new version of Exchange, and I made some assumptions I should not have made when purchasing the new server.  Thank you very much for your advice.
hecgomrecNetwork Administrator

Commented:
Is always a pleasure to help and pass knowledge.

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