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&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 > 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<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/> > 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 ~
