The reason for this is that the design of the databases in Exchange 2010 has been changed very much so from prior releases.
In prior releases you had a single table for messages, a single table for attachments, and so forth. This leads to A LOT of random I/O which is very expensive, especially on slower drives. In Exchange 2010, you have one table _per mailbox_ for folders, one per mailbox for message headers, and one per mailbox for bodies and so forth. What you get from this is huge gains in large sequential I/O because you have contiguous data. The page size has also been increased to 32KB (4-fold increase) which gets you a substantial reduction in I/O operations. Say you have a 26KB message. That's 4 reads in 2007, 1 read in 2010. If you're running in a scenario where you have high availability (the new DAG [Distributed Availability Group] design), the checkpoint depth has been increased substantially which gets a huge reduction in write operations. The build of Exchange 2010 that's available to the public now has a roughly 70% reduction in total IOPS per second. The numbers I'm looking at are for a scenario with 3000x250MB mailboxes with a very heavy user profile and 3MB of cache (RAM) allocated per user. That is a /huge/ performance gain. The net result here is that you can buy fewer cheaper disks, put substantially more users on them (think potential factor of 3-4), and deliver larger mailbox quotas. That's a win. Thanks, Brian Desmond br...@briandesmond.com c - 312.731.3132 -----Original Message----- From: Ben Scott [mailto:mailvor...@gmail.com] Sent: Thursday, May 28, 2009 5:13 PM To: NT System Admin Issues Subject: Re: Amusing On Thu, May 28, 2009 at 5:50 PM, Brian Desmond <br...@briandesmond.com> wrote: > If 3,000 users all come after the same data in a short time window it's going > to be > in the cache which means it's served out of memory (not disk). RAM is way > faster than disk. Except that, from what you're saying, in Exchange 2010, there's no SIS, so there will be no benefit from caching stuff in RAM, because everybody has a unique copy of everything. Tell me again how this is an improvement? -- Ben ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
