DB size recommendation

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John JY

Hi all,

In exchange 2003, for eash database, it's recommended that the size should not exceed 100GB and in exchange 2007 , the recommneded size for each database should not exceed 150GB (200GB for CCR). So, in exchange 2010,
what's the recommended size for each DB? (can support up to 2TB) How about
recommended log size for exchange 2010?

Thank you.

Shafaquat Ali

Hi ,

As per Microsoft !

Exchange 2010 Microsoft has suggested a maximum database size of 2TB! The explanation: With the significant core improvements made to Exchange 2010, the maximum recommended mailbox database size has increased from 200 GB in Exchange 2007 to 2 TB in Exchange 2010.


Shafaquat Ali.

M.C.I.T.P Exchange 2007/2010, M.C.I.T.P Windows Server 2008, M.C.T.S OCS Server 2007 R2, Phone: +923008210320

John JY

Hi Shafaquat,

Thank you for that.
>the maximum recommended mailbox database size has increased from 200 GB in >Exchange 2007 to 2 TB in Exchange 2010

Is size of 2TB too large for recovery(if needed)? If it's 2TB size in DB, what's the recommended log size?


Let me add on this just a little bit, it's important:

Exchange 2010 allows you to deploy larger mailboxes, and the recommended maximum mailbox database size has been increased from 200 gigabytes (GB) in Exchange 2007 to 2 terabytes (when three or more mailbox database copies are being used).


If you are not using a DAG(please review the link and view the topic, "Exchange Native Data Protection"), then recoverability is very relevant and you can forget the 2 TB number. You need to determine maximum database size based on your own SLA's not to exceed 2TB.


John JY

Great help.

From link mention, 3 or more DB copies are being used. Do we have to include lagged database copy?

What is difference between lagged database copy and regular database copy?

Thank you.


I'm not sure what the Microsoft answer is, but to me if you want to do away with database backups in the traditional sense, then a lagged copy is necessary.

So, normal dag members that are hosting a copy of a database get the transaction logs shipped to them and they apply them to there database files, there by bringing there passive copies of database A to the same level as the active copy of database A. A lagged copy protects you from a specific situation:

If a log file is corrupt and is sent to all DAG members, it will corrupt all 3 databases. A lagged copy is special though, you configure it to NOT commit transaction log files until a certain amount of time has passed. The maximum value is 14 days. That means even if all your normal DAG database copies get corrupted, you can do a point in time roll-forward on the lagged copy till the time just before the corruption happened.

Make sense? Using a lagged copy and going through this process is a little bit manual, if you get Data Protection Manager for Exchange then it is fully automated (or close to it, much much easier at any rate).


Neil Hobson [MVP]

The other thing worth mentioning regarding database size is what happens if you have to reseed a database? It is going to take a while to reseed 2TB. Just factor that into your SLAs; there may not be any harm in having more smaller databases (OK, so there will be more LUNs, etc)

"John JY" wrote in message news:928d62d1-abcb-4c22-9dca-dfd14a013d37@communitybridge.codeplex .com...

Great help.

From link mention, 3 or more DB copies are being used. Do we have to include lagged database copy?

What is difference between lagged database copy and regular database copy?

Thank you.
Neil Hobson, Exchange MVP

John JY

Thank you for ALL your help.

Can anyone share what max. size and log you configure in your envir. ?




For stand-alone Mailbox servers (no DAG), keep your databases smaller than 200 GB.

For Mailbox Servers in a DAG (mailbox resilency), keep your databases smaller than 2 Terrabytes.

So here it is, you have 1200 users:

12 Databases, 100 users in each database
Maximum Mailbox Size = 2 GB Maximum Database Size = 200 GB # of Databases = 12

So, that takes care of database LUN's, lets talk about transaction logs. I'm assuming that logs will be cleared at least once daily:
Tlogs Generated per user per day, 3600 Overhead Tlog Generation, 1000 Approximate TLog Generation per day per database: 4.6 GB

So, 20 GB's of storage space per database should cover it, or 240 GB's total just for Tlogs.

Quite honestly, database size and storage design is a per organization type deal. It's very tough to have a cookie cutter type design that accounts for everything in every environment, especially through a forum board. Take what I wrote with a healty dose of skeptisim concerning whether or not it is applicable in your environment.


John JY

Thank you very much.

I am thinking about at corp site: one CAS array (two CA/HUB servers) one CAS server at DR site
One DAG (two mailbox servers at corp site and one mailbox at DR site)
mailbox Server at DR site will hold all DB passive copies. two mailbox servers at corp site will
have 6 active and 6 passive copy each other.

do you see any problem with this design? I propose JBOD (SATA disks) and am not sure whether it will get approved or not?

the upper management still prefer F/C disks.

Thanks again for your sharing.



What is the bandwidth between the two sites? What type of connection is it? What other traffic utilizes it? What is the utilization of the link right now?

I ask because log shipping between sites does eat up bandwidth, and there are latency requirements as well. For a DAG, the round trip ping time from any server in one site must be less than 250 milliseconds. That is the absolute highest it can be, much better for it to be lower.


Brian Day MCITP [MVP]

do you see any problem with this design? I propose JBOD (SATA disks) and am not sure whether it will get approved or not?

JBOD shouldn't be used at your DR stie because if the primary site fails you are left with zero resiliency at your DR site. JBOD is only considered ok as long as you have 3+ HA (non-lagged) copies of the database(s) org-wide and within each datacenter JBOD is only ok if you have at least 2+ HA (non-lagged) copies the datacenter.Brian Day, Overall Exchange & AD Geek
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Microsoft MVP, Exchange Server

John JY


We have around 50 mbps connection. Now, no application runs on this connection. Only, whe the corp site is destroyed and several apps will run at DR site.


wow, nice connection. This is really tough to give you numbers on, if I was a part of your org I would do some testing right now just to make sure I know how much storage is being used for t-logs per day AND when were the peak times for that utilization.

I "think" you would be ok, but that is far from an endorsment. You have to look at your own environment and all the things that would happen in a failover scenario and then make sure utilization and all will work day-to-day and during a DR scenario AND during a rebuilding phase. Reseeding databases and all that can be quite intensive too.

I think your questions have been throughly answered, if you wouldn't mind marking posts as helpful/answers, much appreciated.

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