I'm looking to migrate from our Exchange 2003 servers to Exchange 2007 SP3 running on Windows Server 2008 R2 (Virtual Servers). I'm planning on having two mailbox servers, each with 6Gb RAM and one vCPU hosting around 1000 mailboxes each across 4 Storage Groups (2 on each server). I've had to use the latest ESE files from Exchange 2010 as the current version of JetStress does'nt work, not sure if that is an issue. However, I've ran the Disk subsystem performance test simultiniously across the two servers and, after a bit of tweaking with LUN locations they pass wth flying colours at 1 thread per database (4 in total). Is that maybe too low? When it comes to running the Mailbox profile test it fails, badly. I set the criteria to a 1000 mailboxes on each srever at 1 thread per mailbox and I'm achieving around 102 IOPS but its target is a 1000!! I don't fully understand the thread count so maybe I'm aiming too high here, has anybody got any ideas as to how I can improve the IOPS with this test?. Is my thread count too hig? I'm very keane to get 2007 in but I want to make sure it is running at optimal performace before I do the transition. Just a little background information. The Exchange DB and LOGS are stored on a NetApp SAN, across two different aggregates. The DB is on the aggregate with the most disks and the LOGS on the one with the least, bot are fibre channel disks. The LUN sizes for the DB is 100Gb with an 82Gb DB and for the LOG LUN it's a 20Gb LUN. Both have ample space I would have thought for this testing. Our current Exchange 2003 Organisation has 1950 mailboxes with around an average of 85Mb Our mailboxes range from a staggering 4Gb!!! to 10-20Mb). Now, not all of those mailboxes are used, some are system mailoboxes, service accounts etc etc. We probably only have around 100 active users at any given time time during the working day. I was just thinking maybe I've got my numbers totally wrong for the mailbox profile criteria? Thanks in advance for any help you can give me. Julian