Installation guide

C H A P T E R 9 Storage and File Systems
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Note: ESX Server ignores the preferred path when the multipathing policy is set to
mru.
Saving Your Multipathing Settings
Your multipathing settings are saved when shutting down ESX Server normally.
However, we suggest you run the following command, as root, to ensure your settings
are saved, in case of an abnormal shutdown.
# /usr/sbin/vmkmultipath -S
By running this command, your multipathing settings are restored automatically
when you restart your system.
In Case of Failover
When a cable is pulled, I/O freezes for approximately 30-60 seconds, until the SAN
driver determines that the link is down, and failover occurs. During that time, the
virtual machines (with their virtual disks installed on a SAN) may appear unresponsive,
and any operations on the /vmfs directory may appear to hang. After the failover
occurs, I/O should resume normally.
Even though ESX Server’s failover feature ensures high availability and prevents
connection loss to SAN devices, all connections to SAN devices may be lost due to
disastrous events, that include multiple breakages.
If all connections to the storage device are not working, then the virtual machines will
begin to encounter I/O errors on their virtual SCSI disks. Also, operations in the
/vmfs directory may eventually fail after reporting an “I/O error”.
Settings for QLogic Adapters
For QLogic cards, you may want to adjust the PortDownRetryCount value in the
QLogic BIOS. This value determines how quickly a failover occurs when a link goes
down.
If the PortDownRetryCount value is <n>, then a failover typically takes a little
longer than <n> multiplied by 2 seconds. A typical recommended value for <n> is 15,
so in this case, failover takes a little longer than 30 seconds.
For more information on changing the PortDownRetryCount value, refer to your
QLogic documentation.