Software vs. hardware iSCSI for VMware ESX

1. Hardware iSCSI Features and Limitations

Below are some items to consider if you are planning to use the iSCSI hardware intitiator.

1. ESX Server host booting from iSCSI SAN is possible only with hardware iSCSI initiator
2. Multipathing support for failover only, no load-balancing by using multiple QLA4010s
3. Support for VMotion, VMware HA, and VMware DRS
4. Support for RDMs
5. No support for Microsoft Cluster Server
6. No VMware Consolidated Backup over iSCSI

2. Software iSCSI Features and Limitations

Below are some items to consider if you are planning to use the iSCSI software intitiator.

1. No support for booting ESX Server from software iSCSI
2. Software initiator supports only a single storage interface (vmhba40)
3. Multipathing support for failover only, no load balancing by using multiple physical network adapters (NIC teaming)
4. Support for VMotion, VMware HA, and VMware DRS
5. Support for RDMs
6. No support for Microsoft Cluster Server
7. No VMware Consolidated Backup over iSCSI

3. Step to enable MultiPath failover for iSCSI storage

If you plan to use NIC teaming to increase the availability of your network access to the iSCSI storage
array, you must turn off port security on the switch for the two ports on which the virtual IP address is shared.
The purpose of this port security setting is to prevent spoofing of IP addresses. Thus many network
administrators enable this setting. However, if you do not change it, the port security setting prevents failover
of the virtual IP from one switch port to another and NIC teaming cannot fail over from one path to another.
For most LAN switches, the port security is enabled on a port level and thus can be set on or off for each port.