Windows Server 2003 Std. Exchange Server 2003 Enterprise fully patched. PowerEdge 1850 with PowerVault 220 RAID Array. 80 mailboxes Mirrored System drives: C:\Program Files\Exchsrvr Separate Mirror Log partition: E:\Exchsrvr\mdbdata Separate RAID5 Database partition: G:\Exchsrvr\mdbdata priv1.edb = 41,342,024 KB priv1.stm = 17,645,576 KB pub1.edb = 431,240 KB pub1.stm = 137,224 KB
I have created a test bed as above. I am testing disaster recovery times. To perform a full repair on the priv1.edb took 8 hours, which is too long. I thought what might be a good idea is to create another database and put the most important users (bosses and support) on their own; the idea being smaller db: quicker recovery time for those that really need quick recovery.
I have read a Microsoft article that states they recommend new dbs go in new storage groups, until you run out of goes, then you add new dbs to each storage groups as required.
My first question is, is this sensible idea? Any opinions and suggestions appreciated.
My second question, and no advisory I have read is clear about this, is what to do with the Logs for the second storage group. I cannot afford a new partition, so may I just use a new folder structure in the existing Log partition? Will there be a problems I might encounter?
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Let's start with some background information (you may already know this, but I couldn't tell from your post and the exposition might be helpful to someone in the future).
A major reason for the recommendations is performance, and specifically disk performance. This is where the recommendations for separating the OS/Application, the database files, and the log files comes from. What isn't always made clear is that efficiency comes from physical separation. In other words, it doesn't help to have a single RAID5 array that houses all three functional partitions. You want to separate database reads/writes from transactional log writes.
Creating separate Storage Groups means you have the opportunity to have a separate partition for the transactional logs, so you can gain some efficiency there, but only if you can physically separate them.
So, getting back to your questions, I like the methodology of moving users to a new database (independent of whether to use a new Storage Group). You don't have to dismount a store, and users are only offline during their individual move.
A new Storage Group is fine if you wish to do so. If it is possible to physically separate the database and/or log files from all others (meaning separate physical drives), then you'll gain disk performance. If for example you put a new set of log files on the same physical partition as another set, you're still writing the same amount of data on that partition. There are other considerations for Storage Groups as well, including recovery, that need to be taken into account, but as far as where to locate them, that's up to you.
Another recommendation you'll see is to put the log files of one SG on the same partition as the database files of another. That's to lessen the impact of losing one partition, and can help balance the disk I/O, but overall you're still pushing the same amount of data and disk I/O on the shared drives.
I don't know that I've answered your questions, confused the issue, or created more questions - let us know...
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Regards,
Dean T. Uemura Microsoft MVP - Exchange exchangeguy.blogspot.com uemurad@yahoo.com
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