VM instance of Exchange Server on vSphere

Hello,
I'm trying to figure out the best configuration for my virtual Exchange server.  The only consensus I've come to, thus far, is that the VM should be on it's own datastore.  However, some users recommend multiple datastores for different partitions on the Exchange server. What is best practice?
Thanks
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cuiincAsked:
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Paul SolovyovskySenior IT AdvisorCommented:
Depends on the Exchange size, drive used, array type, etc.. What hardware are you running and how is your storage partitioned?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
What storage are you using for your virtual server?
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aa-denverCommented:
Exchange 2010 and 2013 can tolerate slower disk drives so I have seen people using virtual hard disks VHD for storage.  But I think many of us who have been around for a long time prefer to use more robust storage and raw device mapped RDM drives.  If your server is supporting only 100-200 mailboxes, you could do that with a single VHD and database.  If you are not using multiple database copies, DAG, I would suggest using separate drives for the database and the logs.  If the database drive crashed or became corrupted, you can restore the database from backup and then replay the logs from the separate log drive.  

One of the issues with VHDs for Exchange on SANs is that people often do thin provisioning for the disks.  In a large environment you should get better performance with thick provisioning and separate drives for databases and logs.  Database access is random disk access and log drives are sequential file writes.  Separate drives for each work better in my experience.  

In any case, even with a small number of users, I would use at least one drive for the OS and a second drive for the database and logs.  You don't want the OS drive filling up with a database and shutting down the server.  

If you have a large number of users, say 1000+, I would recommend using more than one database.  If you ever have to restore a database then you do not affect all your users at once and since the database is smaller it takes less time to restore.  

For several thousand users I recommend multiple RDM drives for database and logs.  This is straight forward in VMware if you are using either iSCSI or fibre channel.  You can attach additional drives to the server using drive letters, but I prefer to mount them in a folder on the C: drive.  This does not affect performance.  Example, if my server had two databases I would have 4 drives mounted in folders such as C:\DB-01, C:\DB-02, C:\LG-01, C:\LG-02.   Two drives (folders) each for databases and logs.  IMO this makes administration easier and it is scaleable.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
RDM versus VMDK performance

Conclusion: VMFS and RDM have similar performance. Don’t choose RDM for performance.
Source:http://www.vfrank.org/2011/03/22/performance-rdm-vs-vmfs/

Thin Disks are not supported.
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cuiincAuthor Commented:
Thanks for the info so far, everyone.  In answer to the first 2 questions:

"What hardware are you running and how is your storage partitioned?" and "What storage are you using for your virtual server?"

I am utilizing a Dell PS6100 Equallogic SAN for storage.  I contains 23 1 TB drives (21 RAID members and 2 spares) configured in RAID 50.  This gives me a total of 14 TB.  I have already created a few thick- and few thin-provisioned volumes for SQL and file servers.  At this point, I believe everything is RAID 50, by default.  When I create new volumes, I'm able to choose or modify my RAID config for that volume, although I'm not really sure how that works.  I've been sticking with "default" which i assume is RAID 50.

My current Exchange server databases total around 600 GB.  

If thin provisioning is not supported, i need to make sure i give myself enough headroom when i create the volumes.  I'm not sure how much room I should give to the LOGS volumes versus the database volumes.  Previously, in my environment, they've existed on the same hard drive, so i'm not sure the size requirements of the logs.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
It's Virtual Machine Disks (VMDK) Thin Provisioned which are not supported.

Logs and DBs in your environment, are going to be stripped across all disks, so similar performance, unless you start tweaking RAID type for luns.
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cuiincAuthor Commented:
thanks-- how best do i determine how big to make my log versus DB volumes?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
How  many users and what size mailboxes are you going to allocate
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cuiincAuthor Commented:
60 - 100 users.  mailboxes currently run all the way up to 30 GB, although the average is about 10 GB.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
If everyone has a mailbox at 30GB * 100, you can see where this is going.

So if the average is 10, 10GB x 100 = ???? for your DB LUN

Do you not give anyone a quota?
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cuiincAuthor Commented:
thanks; what about the volume size for the logs?  what proportion of the db volume size should the log volume be?

i'm coming into this situation rather suddenly, and--since these users utilize their mailboxes as their primary business correspondence--i am still unsure how to balance this situation.  users need their historical records, but we need a speedy server.  i'm hoping that exchange 2010 provides better archiving solutions for us.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Logs transaction sizes, are based on the rate of change of how many emails are being sent and received a day, for that mailbox store.

I would work on 10-15% of the DB size LUN.
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