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Could a storage bottleneck be causing Microsoft Exchange server to be slow?

Applies to

Microsoft exchange server 2003

Answer

Typically, to determine if the performance issue is storage related, we need to determine if the Exchange host is seeing any latency from the Logical Unit Number (LUNs) that are mounted. From the Exchange host use the Perfmon tool that is included in Windows. Unless Perfmon is showing latency on those virtual disks, the performance issue is typically on the host and not the filer. Please start a Perfmon session on the Exchange host and add the following counters:

 
  • PhysicalDisk\\Average Disk sec/Read
  • PhysicalDisk\\Average Disk sec/Write
  • PhysicalDisk\\Average Disk Queue Length
 

Microsoft has defined the following guidelines for the functions that those disks serve as values for the counters:

 

Database
PhysicalDisk\\Average Disk sec/Read - These values should average less than 20ms and spikes should be less than 50ms
PhysicalDisk\\Average Disk sec/Write - These values should average less than 20ms and spikes should be less than 50ms
PhysicalDisk\\Average Disk Queue Length - Please note this value

 

Transaction Logs
PhysicalDisk\\Average Disk sec/Read - These values should average less than 5ms and spikes should be less than 50ms
PhysicalDisk\\Average Disk sec/Write - These values should average less than 10ms and spikes should be less than 50ms
PhysicalDisk\\Average Disk Queue Length - Please note this value

 

SMTP queues
PhysicalDisk\\Average Disk sec/Read - These values should average less than 10ms and spikes should be less than 50ms
PhysicalDisk\\Average Disk sec/Write - These values should average less than 10ms and spikes should be less than 50ms
PhysicalDisk\\Average Disk Queue Length - Please note this value

 

Page File Disk
PhysicalDisk\\Average Disk sec/Read - These values should average less than 10ms and spikes should be less than 50ms
PhysicalDisk\\Average Disk sec/Write - These values should average less than 10ms and spikes should be less than 50ms
PhysicalDisk\\Average Disk Queue Length - Please note this value

 

Note:
The page file disk should on local storage if it is not currently located there. See the technical report, SAN Booting with Windows Server Operating Systems, for more information on SAN booting hosts.

 

The following counters are not storage specific, but will provide information about how the host is processing Microsoft Exchange requests. It can also help to pinpoint a host-side issue.

 
  • Memory\\Available Mbytes (MB)
  • Memory\\Pages/sec
  • Processor\\% Processor Time (_Total)
  • System\\Processor Queue Length
  • Network Interface\\Bytes Total/sec
  • Network Interface\\Packets Outbound Errors
  • SMTP Server\\Categorizer Queue Length
  • MSExchangeDSAccess Process\\LDAP Read Time (for all processes)
  • MSExchangeDSAccess Process\\LDAP Search Time (for all processes)
 

From the filer, issue the sysstat command to see what it is doing in real-time.The sysstat output can be used in conjunction with the Perfmon output, to quickly see if a the problem exists on the host-side only. It can also be used to see if the filer is showing signs of a bottleneck. In a Storage Area Network (SAN) environment, use the -f (FCP) or -i (iSCSI) optionscan to get additional output.

 

If the Perfmon output shows excessive latencies and the sysstat output shows low disk, and respective protocol utilization, then there is not a backend storage bottleneck and additional host-side configuration troubleshooting may be required with assistance from Microsoft.

 

If the Perfmon output shows excessive latencies, and the sysstat output reflects high disk and protocol utilization as well, then you likely have a storage bottleneck. In these cases, please call the NetApp support for additional assistance.

 

Related Links:
Troubleshooting Exchange Server 2003 Performance
Sysstat manpage
3012662: Collecting data to diagnose an Exchange 2000 or 2003 performance problem
3013882: Top 10 SnapManager for Microsoft Exchange Server issues and solutions

Additional Information

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