Hi Exchange Gurus, Need opinions to think thru the logs/DBs configuration for our Exchange environment. We have two servers running in an active/passive DAG setup. The DAG will host about 2000 users with average 50 users per day. Each server will have 12GB memory. For the logs, I am planning to have one dedicate LUN for all the logs. Will there be any performance or fragmentation issue? For the DBs, the best practice is to have dedicate LUN for each DBs but I am thinking about the cost/benefit for using dedicated LUNs. E.g. If I have 4x500GB internal SAS disks as RAID5. I have 1.5TB effective space. Is it better to allocate 5 x 300GB LUNs and use mount point to host them in one drive letter. Or allocate a big 1.5TB LUN shared by all 5 DBs? As far as disk space growth management is concerned, one big LUN is much easier to manage and best utilized than 5 smaller LUN but will there be any performance or fragmentation issue? Thx

Hi Have you used mailbox role calculator? If not, do it, it will help you calculating on storage http://msexchangeteam.com/archive/2009/11/09/453117.aspx http://msexchangeteam.com/files/default.aspxJonas Andersson MCTS: Microsoft Exchange Server 2007/2010 | MCITP: EMA 2007/2010 | MCSE/MCSA Blog: http://www.testlabs.se/blog

I am more curious whether sharing mutliple DBs and LOGs in one big LUN instead of individual small LUNs will create serious fragmentation issue. It is much more easiest to manage space growth for one LUN than multiple LUNs. I think the performance is limited by the number of spindles, so I think the key issue here is external fragmentation.

The thing I've heard with 2010 is that you can have both DB and LOGs on same LUN 2010 handles the I/O better than before and doing more sequential writings than before This didn't answer your question but a suggestion is to have both DB and LOGs on same LUN and split them into different LUNs I understand your concerns about the manage of the storage/LUNs will be easier if there is only one Jonas Andersson MCTS: Microsoft Exchange Server 2007/2010 | MCITP: EMA 2007/2010 | MCSE/MCSA Blog: http://www.testlabs.se/blog

"E.g. If I have 4x500GB internal SAS disks as RAID5. I have 1.5TB effective space. Is it better to allocate 5 x 300GB LUNs and use mount point to host them in one drive letter. Or allocate a big 1.5TB LUN shared by all 5 DBs" You're making this harder on yourself than it has to be. Why would you have 5 databases? The max recommended size is 2TB. You can have the logs on the same LUN as the database as long as you will not be using a VSS backup. By the way, how did you intend to back it up? If you plan to use VSS, then you need seperate LUNs for the logs and database. If you intend to use Exchange Native Protection, you can have one LUN for both the logs and database. If ENP is your intent, you're short a copy or two. You really should go get the Exchange 2010 Mailbox role storage caclulator and run the varios configurations. It'll make things a lot easier. J

Hi, I normally use third party backup software so in that case I recommend using a seperate LUN for the Logs. Depending on the load your users have on the servers I would recommend that you create one 1,5 TB Drive for the databases and then keep them as 5 so the restore period will be less per database. /Martin

Hi John, Correct me if I am wrong. Are you suggesting 1 big database on one big 2TB LUN? Problem is the restore time in case DAG is not sufficient to prevent db restore. Also I think that may have performance impact. I believe Microsoft has dropped backup API on Exchange 2010 and we are not using any fancy virtual backup strategy, so 3rd party Exchange-aware VSS will be our primary choice, we are also thinking to use 3rd party VSS on one copy, and DPM on the remote site. Oh, what's ENP stand for?

Hi Martin, so you recommend one big LUN for all the logs and one big LUN for 5 databases? I really like this approach but any risk of external fragmentation? Thx

Hi, Yes one LUN for Logs, how large it has to be depends on your mailflow, and one large LUN for the databases. I haven't seen any issues with fragmentation because I have more databases on one LUN over having the spread out. The one with that speaks for more LUNs is that you can minimize downtime for other databases if just one LUN gets an error. /Martin

So fragmentation is not an issue at all? I think the risk of LUN failure is small since it is RAIDed anyway, plus mirrored to another site.

I haven't had any reason to defragment after getting to Exchange 2007 and Exchange 2010. As you write with RAID and mirrored site the benifits of small LUNs doesn't come into play with you. I would definently go with the big LUN for the databases. /MartinExchange is a passion not just a collaboration software.

One big database as long as you're under the 2TB limit. Backup/restore: You have two options, let's take a look. Option 1: Exchange Native Backup. You need at least a third copy of the data and probably an additional LAG copy. The advantage is you can put logs on the same LUN as the database. Option 2: VSS Backup. Streaming backups via the old backup API are no longer supported. It's a snap and replicate type of thing be it Backupexec or DPM or whatever. You have two copies of the data in the DAG. Should one fail, you can either do a full reseed from the remaining copy, or stage a snapshot restore and do an incremental reseed. If both your copies go down at the same time (the DAG was designed to protect against this because you have seperate servers, storage, etc), then you are in for a longer outage; arguably one that is unavoidable in that you had multiple harware failures bringing all your DAG nodes down. If you use VSS, the logs and databases need to be on seperate LUNs. J