I use the Microsoft definitions:
For light users (which are defined as 5 sent messages/20 received messages per day), allocate 2.0 MB per mailbox. For average users (defined as 10 sent messages/40 received messages per day) allocate 3.5 MB per mailbox. For heavy users (defined as anything over average) allocate 5.0 MB per mailbox. Obviously, calculating this for each user would be practically impossible, so it is best to guesstimate your average user plus a fudge factor. Regards, Michael B. Smith, MCITP:SA,EMA/MCSE/Exchange MVP My blog: http://TheEssentialExchange.com/blogs/michael Link with me at: http://www.linkedin.com/in/theessentialexchange From: Jonathan Link [mailto:[EMAIL PROTECTED] Sent: Friday, October 03, 2008 8:50 AM To: MS-Exchange Admin Issues Subject: Re: Quick Question Can you define heavy use? On Thu, Oct 2, 2008 at 11:03 PM, Michael B. Smith <[EMAIL PROTECTED]> wrote: Obligatory Warning: This post uses basic math! <gasp> It also serves to show why, while the OP thought this was a quick question, it really is not. Even with small servers and small numbers of users, you have to pay attention to the I/O subsystem. I've gone into far too many SBS customers who thought their SBS server with SATA disks should support 10 users just fine. Well, it really depends. I covered the performance calculation for RAID-1 and RAID-5 on SCSI and SATA recently in the eZine EMO: http://peach.ease.lsoft.com/scripts/wa.exe?A2=ind0809 <http://peach.ease.lsoft.com/scripts/wa.exe?A2=ind0809&L=EMO-NEWSLETTER&T=0&; F=&S=&P=1470> &L=EMO-NEWSLETTER&T=0&F =&S=&P=1470 I added some more information about how this effects SANs here: http://theessentialexchange.com/blogs/michael/archive/2008/09/19/it-s-all-ab <http://theessentialexchange.com/blogs/michael/archive/2008/09/19/it-s-all-a bout-the-iops-silly.aspx> out-the-iops-silly.aspx I cover this particular question (the performance required of disk subsystems for Exchange and how that is affected by disk choice, controller choice, SAN choice, etc.) in great depth in my upcoming book "Exchange Server 2007: Operations and Monitoring". That's my commercial. :-) Using RAID-1, read performance is equal to (IOPS * N), where N is the number of disks in the array and IOPS is the total IOPS available from a single disk. Write performance is (IOPS * N / 2). Note that N must always be an even number (such as 2, 4, 6, 8.) with RAID-1. However, the amount of disk available is (GB * N / 2), where GB is the amount of disk space available on a single disk. Using RAID-5, read performance is equal to (IOPS * (N - 1)). Write performance is (IOPS * ((N - 1)/ 4)). Note that N can be any number higher than 2. The amount of disk space is (GB * (N - 1)). For 40 heavy users, your database IOPS requirement is about 20 IOPS. Your transaction log IOPS requirement is about 8 IOPS. We will exclude the operating system and page file IOPS requirement as best practice requires that they be on separate volumes/arrays than any Exchange array. (Given the proper amount of memory in a server, Exchange will not page significantly; and after cache is steady-stated, I/O requirements of the operating system are quite small.) Your average 7,200 RPM SATA drive will only provide you with approximately 35 IOPS (this is called a "full stroke" IOPS, required for any random access application, as opposed to sequential read/write). In RAID-1 (two disks), your Read IOPS is 70, however your Write IOPS is still only 35 IOPS! Assuming Exchange 2007, with approximately a 1:1 read:write ratio, your average IOPS is 52.5. In RAID-5 (three drives), your Read IOPS is 70 IOPS and your Write IOPS is 17.5 IOPS. Average IOPS is 44 IOPS. RAID-5 does meet the I/O requirements for 40 heavy Exchange users with those drives. However, during times of heavy database update, the disk drives will be unable to keep up and Exchange performance will degrade. I would not provision RAID-5 in this configuration. If you are configuring a single Exchange server (that is, one that holds all the Exchange roles), you should consider bumping the memory to 4 GB (the calculation actually comes to 3.2 GB, but that would be pretty hard to find!). Regards, Michael B. Smith, MCITP:SA,EMA/MCSE/Exchange MVP My blog: http://TheEssentialExchange.com/blogs/michael Link with me at: http://www.linkedin.com/in/theessentialexchange -----Original Message----- From: Martin Blackstone [mailto:[EMAIL PROTECTED] Sent: Thursday, October 02, 2008 10:15 PM To: MS-Exchange Admin Issues Subject: RE: Quick Question Those 1 TB drive are SATA I'm sure so they may be overkill size wise, they are not performance wise. -----Original Message----- From: Jason Tierney [mailto:[EMAIL PROTECTED] Sent: Thursday, October 02, 2008 6:29 PM To: MS-Exchange Admin Issues Subject: RE: Quick Question I would just throw them in a single RAID5 and make a 40GB Windows partition and put everything else on the other partition. Specs are made for servers that hold hundreds of users. For 30-45 users, your 4 1TB drives are overkill anyway. Get a decent proc and 2-3GB of RAM and you'll have no troubles at all. Jason Tierney, MCITP:EA Vice President, Consulting Services Corporate Network Services "Count on Us" 20010 Fisher Ave, Suite E Poolesville, MD 20837 direct: 240-425-4441 | main: 301.948.8077 | fax: 301.349.2518 http://www.cornetser.com <http://www.cornetser.com/> <http://www.cornetser.com/> Best Place to Work, Alliance for Workplace Excellence - 2006, 2007, 2008 ...ask me how to better manage your IT costs with PROSuite ~ Ninja Email Security with Cloudmark Spam Engine Gets Image Spam ~ ~ http://www.sunbeltsoftware.com/Ninja ~ ~ Ninja Email Security with Cloudmark Spam Engine Gets Image Spam ~ ~ http://www.sunbeltsoftware.com/Ninja ~
