How to tell if the disks are I/O limited

Suboptimal disk layout and allocation can lead to poor performance of the Tealeaf® components. Use the informationin this topic to determine if your disks are creating a performance bottleneck.

At http://support.tealeaf.com/, Solution 65 "Configuring the RAID Hard Disk Drive (HDD) Array" goes into detail about the best way to configure the physical disks into arrays and explains the reasons behind the recommendations. If your server is not laid out according to these practices, the Tealeaf system performance may be disk I/O-bound.

This solution explains how to determine if your disks are creating a performance bottleneck:

• Run the Windows PerfMon utility.
• If the Average Disk Queue Length counter is not already displayed, right-click the right pane and select Add counters.
• In the Performance Object drop-down, select Physical Disk.
• In the rightmost set of radio buttons, select All instances.
• In the left pair of radio buttons, select Select counters from list.
• Multi-select the following three counters from the list box:
  • Avg Disk Queue Length
  • Avg Disk Read Queue Length
  • Avg Disk Write Queue Length
• Click Add.
• Look at the results in the perfmon right pane.
• Focus on the disks that house the CANISTER, dbs directory, and the Indexes directory.
  • Average queue lengths should be less than 1.
  • Queue lengths of 4 or greater mean the disk is I/O bound.

Average queue lengths of 4 or more are a strong indication that the system's disk drives need repartitioning along the guidelines of Solution 65.

If your system is configured according to Solution 65 standards, does not use RAID, and has high average queue lengths, the solution is to move to a faster disk subsystem or add additional Tealeaf servers. The current system does not have the disk I/O bandwidth to handle the data processing load that is presented to it.