Hi All Im currently planning our Exchange migration from 03 to 2010 and I am aware that Exchange 2010 has dropped the single instance store for emails so potentially the amount of storage space needed will increase. But what im trying to work out is how much this is going to increase by? anyone figured this out before? We have about 220gb in Exch 03, when i migrate everyone to the new Exch 2010 servers i presume this is going to blow out, increase but how can i tell how much by? I guess i need to factor in the loss of single instancing for the design of our new mailbox database servers when sizing the data stores but again im not sure how much of an impact loosing single instancing is going to have on us.... anyone help? Cheers Stewart

It could be bigger, but it could also be smaller. Depends on current white space, 2010 actually has compression built in, depends on current SIS ratio, etc. Here is a very similar thread below, not sure if you are going to find a hard answer as it depends a lot on your specific environment. http://social.technet.microsoft.com/Forums/en-US/exchange2010/thread/49fa0bad-ab4f-4330-9b24-bbaaa5443890 Tim Harrington - Catapult Systems - http://HowDoUC.blogspot.com

ahh nice, thanks for the link Tim :)