Mark, Are you sure that's the data you're after? The difficult data to obtain is typically what the system is capable of and not what they're actually doing. DAS storage typically presents an IO ceiling the applications simply cannot exceed. The actual capabilities of disks can be argued, but I've always done well by using the following statistics for IO capabilities by drive: 7.2k RPM = 75-100 IOPS, 10K RPM = 100-150 IOPS, 15K RPM = 150-200 IOPS. This doesn't take into account the other pros/cons between drive types (Fiber Channel, ATA, SAS, etc.) but works for simple math.
Michael gave you some good perfmon counters to monitor. The two I would add is Avg Disk Sec/Read and Avg Disk Sec/Write. This, along with avg queue length, will help you identify what kind of bottleneck your systems may be encountering. Typical thresholds for read/write latencies are avg below 10/20ms and spikes below 50/60ms. Some applications may be more or less sensitive to certain latency but those are decent numbers to work with. Avg queue length is tough to gauge because there seems to be two camps on the subject. There are those that strive for avg queue lengths below 1 and others that feel and avg queue length of N or below (where N = the number of disks serving IO) is a good place to be. As far as total IO, you simply add the avg disk reads/writes per second or max disk reads/writes per second. That depends on if you're spec'ing your SAN to support your sustained IO or your peak IO. Whatever data you're able to collect in terms of IO, I would multiply that by a certain factor if you're looking to increase performance. This practice will help you account for applications that may have been IO constrained by DAS that could end up on high-end storage and consume all of the IO you're able to provide. Now, to use the data to help spec your SAN solution, we would need to know what solutions you're currently entertaining. There are a number of different solutions that all leverage very unique technologies that have changed the game from previous raw storage solutions. Just to share my recent experience, I have migrated approximately 30 servers from an EMC CX700 array to two Compellent Arrays over the last few weeks. We didn't have very in-depth tools to gauge IO requirements but we did our best with the tools at our disposal. One SQL server we migrated had DBs residing on a LUN served by a 7 Disk RAID 5 RAID Group backed by 146GB/10K Fiber Channel disks. This RAID group also served LUNs for 4-5 other SQL servers so disk contention was evident. This SQL server, over a 12 week period, was identified as never exceeding 300 IOPS. After migrating this server to one of our Compellent Arrays backed by 12 SSDs, 36 15K SAS and 24 7.2K NL SAS drives, we saw peak IOPS exceed 5500. This certainly wasn't a common experience during our migrations but we had a few servers that really started to open up after migration. - Sean On Mon, Feb 6, 2012 at 1:56 PM, Reimer, Mark <[email protected]>wrote: > The question is: I want to know what my different servers (no san, each > with their own direct attached disks storage) is using (not what they are > capable of, but what they are actually using/doing). **** > > ** ** > > Sorry if I was unclear to begin with.**** > > > Mark**** > > ** ** > > *From:* Brian Desmond [mailto:[email protected]] > *Sent:* Monday, February 06, 2012 2:55 PM > > *To:* NT System Admin Issues > *Subject:* RE: IOPS's calculations**** > > ** ** > > *Your SAN should be able to produce these numbers. *** > > * * > > *Thanks,* > > *Brian Desmond* > > *[email protected]* > > * * > > *w – 312.625.1438 | c – 312.731.3132* > > * * > > *From:* Reimer, Mark [mailto:[email protected]] > *Sent:* Monday, February 06, 2012 2:56 PM > *To:* NT System Admin Issues > *Subject:* IOPS's calculations**** > > ** ** > > Hi folks,**** > > ** ** > > Thanks for all your help in the past.**** > > ** ** > > Looking at setting up a SAN. From my research, I think one thing to be > aware of is current IOPS (disk). There are a number of sites that will help > you determine IOPS based on what hard drives (and RAID configuration). My > question is: Many of my current servers are light use. The IOPS that these > servers are capable of is much greater than what is actually being used.** > ** > > ** ** > > So, in order to more properly size the SAN, is there a way to determine > working IOPS? That is, what is actually being used? I assume Perfmon would > help, and will need to log over a period of time (I think a week would be > about right, to catch most scenarios). But what counters, and how to > analyze those counters?**** > > ** ** > > Servers are Windows 2003.**** > > ** ** > > Thanks.**** > > ** ** > > ** ** > > Mark Reimer, A+, MCSA**** > > Servers & Networking Admin**** > > Prairie Bible Institute**** > > Box 4000**** > > Three Hills, AB T0M-2N0**** > > Canada**** > > Tel: 403-443-5511, Ext. 3476**** > > Fax: 403-443-5540**** > > Email: [email protected]**** > > www.prairie.edu**** > > ** ** > > ** ** > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ > ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ > > --- > To manage subscriptions click here: > http://lyris.sunbelt-software.com/read/my_forums/ > or send an email to [email protected] > with the body: unsubscribe ntsysadmin**** > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ > ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ > > --- > To manage subscriptions click here: > http://lyris.sunbelt-software.com/read/my_forums/ > or send an email to [email protected] > with the body: unsubscribe ntsysadmin**** > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ > ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ > > --- > To manage subscriptions click here: > http://lyris.sunbelt-software.com/read/my_forums/ > or send an email to [email protected] > with the body: unsubscribe ntsysadmin > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to [email protected] with the body: unsubscribe ntsysadmin
