vsphere-esxi-vcenter-server-55-storage-guide

vSphere Storage• “Configuring CHAP Parameters for iSCSI Adapters,” on page 92• “Configuring Advanced Parameters for iSCSI,” on page 95• “iSCSI Session Management,” on page 97ESXi iSCSI SAN RequirementsYou must meet several requirements for your ESXi host to work properly with a SAN.• Verify that your SAN storage hardware and firmware combinations are supported in conjunction withESXi systems. For an up-to-date list, see vSphere Compatibility Guide.• Configure your system to have only one VMFS datastore for each LUN.• Unless you are using diskless servers, set up a diagnostic partition on a local storage. If you havediskless servers that boot from iSCSI SAN, see “General Boot from iSCSI SAN Recommendations,” onpage 107 for information about diagnostic partitions with iSCSI.• Use RDMs for access to any raw disk. For information, see Chapter 17, “Raw Device Mapping,” onpage 155.• Set the SCSI controller driver in the guest operating system to a large enough queue. For information onchanging queue depth for iSCSI adapters and virtual machines, see vSphere Troubleshooting.• On virtual machines running Microsoft Windows, increase the value of the SCSI TimeoutValueparameter to allow Windows to better tolerate delayed I/O resulting from path failover. Forinformation, see “Set Timeout on Windows Guest OS,” on page 219.ESXi iSCSI SAN RestrictionsA number of restrictions exist when you use ESXi with an iSCSI SAN.• ESXi does not support iSCSI-connected tape devices.• You cannot use virtual-machine multipathing software to perform I/O load balancing to a singlephysical LUN.• ESXi does not support multipathing when you combine independent hardware adapters with eithersoftware or dependent hardware adapters.• ESXi does not support IPv6 with software iSCSI and dependent hardware iSCSI.Setting LUN Allocations for iSCSIWhen preparing your ESXi system to use iSCSI SAN storage you need to set LUN allocations.Note the following points:• Storage Provisioning. To ensure that the host recognizes LUNs at startup time, configure all iSCSIstorage targets so that your host can access them and use them. Also, configure your host so that it candiscover all available iSCSI targets.• vMotion and VMware DRS. When you use vCenter Server and vMotion or DRS, make sure that theLUNs for the virtual machines are provisioned to all hosts. This configuration provides the greatestfreedom in moving virtual machines.• Active-active versus active-passive arrays. When you use vMotion or DRS with an active-passive SANstorage device, make sure that all hosts have consistent paths to all storage processors. Not doing so cancause path thrashing when a vMotion migration occurs.For active-passive storage arrays not listed in Storage/SAN Compatibility, VMware does not supportstorage-port failover. You must connect the server to the active port on the storage system. Thisconfiguration ensures that the LUNs are presented to the host.76 VMware, Inc.