vSphere Storage - ESXi 5.0 - Documentation - VMware

vSphere Storage
IBM System Storage DS4800 Storage Systems
IBM System Storage DS4800 systems used to be called IBM FAStT. A number of storage array vendors
(including LSI and StorageTek) make SAN storage arrays that are compatible with the DS4800.
For your host to work with IBM DS4800 and other compatible systems, make sure to set the multipathing policy
on your host to Most Recently Used.
Configuring the Hardware for SAN Failover with DS4800 Storage Servers
This topic provides information on how to set up a highly available SAN failover configuration with an
ESXi host and DS4800 storage.
You must have the following hardware components:
n Two FC HBAs, such as QLogic or Emulex, on each ESXi machine.
n Two FC switches connecting the HBAs to the SAN (for example, FC switch 1 and FC switch 2).
n Two SPs (for example, SP1 and SP2).
Each SP must have at least two ports connected to the SAN.
Use the following connection settings for the ESXi host, as shown in SAN Failover:
n Connect each HBA on each ESXi machine to a separate switch. For example, connect HBA1 to FC switch
1 and HBA2 to FC switch 2.
Figure 5-1. SAN Failover
Host 1 Host 2
HBA1 HBA2 HBA3 HBA4
FC switch 1
SP1 SP2
storage
FC switch 2
This configuration provides two paths from each HBA, so that each element of the connection can fail over to
a redundant path. The order of the paths in this configuration provides HBA and switch failover without the
need to trigger SP failover. The storage processor that the preferred paths are connected to must own the LUNs.
In the preceding example configuration, SP1 owns them.
NOTE The preceding example assumes that the switches are not connected through an Inter-Switch Link (ISL)
in one fabric.
Disabling Auto Volume Transfer
To avoid the possibility of path thrashing, disable Auto Volume Transfer (AVT) on the SAN storage processors.
If AVT is enabled, the two storage processors can alternately take ownership of the LUN in certain situations,
resulting in performance degradation. AVT is also known as ADT (Auto Disk Transfer).
To disable AVT, in the DS 4800 Storage Manager, for each port defined in each host group that contains HBAs
for one or more ESXi hosts, set the host type to LNXCL or, in later versions, to VMware.
You must reboot the hosts after you change the AVT configuration.
46 VMware, Inc.