HP 3PAR VMware ESX Implementation Guide
NOTE: VMware and HP recommend the LSI logic adapter emulation for Windows 2003 Servers.
The LSI Logic adapter is also the default option for Windows 2003 when creating a new virtual
machine. HP testing has noted a high incidence of Windows 2003 virtual machine failures during
an ESX multipath failover/failback event when the BUS Logic adapter is used with Windows 2003
VMs.
NOTE: HP testing found that the SCSI timeout value for virtual machine guest operating systems
should be 60 seconds to successfully manage path failovers at the ESX layer. Most guest operating
systems supported by VMware have a default SCSI timeout value of 60 seconds, but this value
should be checked and then verified for each GOS installation. In particular, Red Hat 4.x guest
operating systems should have the SCSI timeout value changed from the default 30 seconds to 60
seconds.
Use the command line to set the SCSI timeout on all SCSI devices presented to a Red Hat 4.x virtual
machine to 60 seconds:
find /sys -name timeout | grep "host.*target.*timeout" | xargs -n 1
echo "echo 60 >"|sh
Add this line in the /etc/rc.local file of the Red Hat 4.x guest OS to maintain the timeout
change with a virtual machine reboot.
Example of a modified /etc/rc.local file:
# cat /etc/rc.local
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
find /sys -name timeout | grep "host.*target.*timeout" | xargs -n 1 echo "echo 60 >"|shtouch /var/lock/subsys/local
On Windows Server, check the TimeOutValue using the following command:
C:\ reg query HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\disk /v TimeOutValue
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\disk TimeOutValue REG_DWORD 0x3c
Multipath Failover Considerations and I/O Load Balancing
NOTE: This section about multipathing and configuring to Round Robin policy applies to all
connectivity types: FC, FCoE, and iSCSI.
VMware ESX 3.0 - 3.5 includes failover with multipath support to maintain a constant connection
between the ESX host and the HP 3PAR StoreServ Storage array. VMware terms this multipath
support with a choice of two path policies called Fixed or MRU. Starting with ESX 4.0, a third
path policy choice of round robin is available. The path policies can be modified on a
per-HP 3PAR StoreServ Storage-volume (LUN) basis by right-clicking the device listing and selecting
the Properties function from the VI/vSphere client menu. A pop-up window allows you to 'manage
paths so that the properties of the paths to the volume selected can be modified. Using this control,
you can select the path policy, and specify which path is the active preferred path to a volume on
the storage array, or which path is the standby path within the Fixed path policy scheme.
Additionally, paths can be disabled to prevent any traffic over a specific path to a volume on the
storage array.
Multipath Failover Considerations and I/O Load Balancing 39