Specifications

VMware, Inc. 277
Chapter 9 Storage and File Systems
Saving Your Multipathing Settings
Your!multipathing!settings!are!saved!when!shutting!down!ESX!Server.!However,!
VMware!suggests!that!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)!might!appear!
unresponsive,!and!any!operations!on!the!/vmfs!directory!might!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!can!be!lost!due!to!
disastrous!events,!that!include!multiple!breakages.
If!all!connections!to!the!storage!device!are!not!
working,!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!can!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>,!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.
N
OTE ESX!Server!ignores!the!preferred!path!when!the!multipathing!policy!is!set!to!mru.