6.5.1

Table Of Contents
Solution
1 If the sum of active commands from all virtual machines consistently exceeds the LUN depth,
increase the queue depth.
The procedure that you use to increase the queue depth depends on the type of storage adapter the
host uses.
2 When multiple virtual machines are active on a LUN, change the Disk.SchedNumReqOutstanding
(DSNRO) parameter, so that it matches the queue depth value.
Adjust Queue Depth for QLogic, Emulex, and Brocade HBAs
If you are not satisfied with the performance of your hardware bus adapters (HBAs), change the
maximum queue depth on your ESXi host.
The maximum value refers to the queue depths reported for various paths to the LUN. When you lower
this value, it throttles the host's throughput and alleviates SAN contention concerns if multiple hosts are
overutilizing the storage and are filling its command queue.
To adjust the maximum queue depth parameter, use the vCLI commands.
In the procedure, --server=server_name specifies the target server. The specified target server
prompts you for a user name and password. Other connection options, such as a configuration file or
session file, are supported. For a list of connection options, see Getting Started with vSphere Command-
Line Interfaces.
Prerequisites
Install vCLI or deploy the vSphere Management Assistant (vMA) virtual machine. See Getting Started with
vSphere Command-Line Interfaces. For troubleshooting, run esxcli commands in the ESXi Shell.
Procedure
1 Verify which HBA module is currently loaded by entering the following command:
esxcli --server=server_name system module list | grep module
Use one the following options for module.
Option Description
qla QLogic
qln QLogic native drivers
lpfc Emulex
bfa Brocade
vSphere Troubleshooting
VMware, Inc. 66