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We have a legacy VMware Server connecting to an NFS datastore that runs two Exchange 2007 servers (edge + hub) on Windows 2003. We are a small org with about 50 users.

We're in the process of moving everything off VMware Server and onto VMware ESXi.

At the time it seemed like flat preallocated disks were preferred for virtualized Exchange instances, but I've noticed that ESXi defaults to thin provisioning for vmdks on an NFS datastore. That has me wondering, which do I use when I convert this machine, thin or flat?

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up vote 2 down vote accepted

When we migrated from ESX to ESXi, we already had an Exchange 2007 environment. Considering the I/O requirements of Exchange, I'd strongly prefer to preallocate instead of going with thin provisioning. Go for flat.

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What about Exchange 2010? I've read that it has something like 90% reduced I/O over 2003/2007. I feel like I'd still rather flat provision Exchange, but is it actually still "better"? – minamhere Nov 18 '10 at 4:29
@minamhere I haven't done enough with Exchange 2010 to be able to accurately guess at is I/O needs. We're going there next, though. Probably with flat files as we've done with everything else. – sysadmin1138 Nov 18 '10 at 6:09

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