Understanding the Relationships between Disk I/O and Application Performance

If you've been a systems administrator for long you've probably dealt with application performance problems that turned out to be caused by disk Input/Output (I/O) performance. Not too many years ago this was why we replaced IDE drives with SCSI arrays when we were building application and/or database servers. Back then we all knew how to build servers by hand and we spent a lot of time under the hood tweatking our servers. Faster disks, more spindles, and wider controller channels were all tools that we'd use to pimp out our servers and get as a much performance as we could.

Nowadays things are a quite bit different. First off, most of our servers are virtual. Adding more CPU or memory is as simple as a few mouse clicks within our virtual system manager of choice. I can't remember the last time I physicall touched a server when trying to make it run faster. Not only are the servers virtual, but the disks aren't physically attached to the physical server. Instead, the disks are set in an array as a part of a Storage Area Network (SAN). You carve up your SAN into LUNs (Logical Unit Numbers) and then assign LUNS to your virtual host servers (VSphere servers from VMWare for instance). VSphere then carves up space on the LUN to the vritual servers that it maintains.

Sounds pretty cool, but what do you do when you're fighting an application performance problem that is related to disk I/O rates and/or latency? How do get you a clear, end-to-end picture of of the infrastructure that makes up the virtual application servers's computing environment and the performance of each component along the way?

In some cases you can get pieces of this information from the virtual system manager and/or the SAN vendor's management software, but to get a complete picture you need an application that's built around providing this functionality - regardless of the types of SANs or servers you're using. As you've probably guessed by now, we here at SolarWinds have such an application - the SolarWinds Profiler. Profiler gives you this end-to-end mapping from the phsical disks, the LUNs, through the network to the virtual server host, and all the way to the virtual server. By leveraging Orion with it you can get an even more complete picture by adding network performance and traffic analysis.

And yes, you can download this and try it for free from SolarWinds.com and have it up and running all by yourself in no time...

Flame on...
Josh
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