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

Chapter 2 Overview of Using ESXi with a SANESXi Hosts and Multiple Storage ArraysAn ESXi host can access storage devices presented from multiple storage arrays, including arrays fromdifferent vendors.When you use multiple arrays from different vendors, the following considerations apply:• If your host uses the same Storage Array Type Plugin (SATP) for multiple arrays, be careful when youneed to change the default Path Selection Policy (PSP) for that SATP. The change will apply to allarrays. For information on SATPs and PSPs, see Chapter 23, “Understanding Multipathing andFailover,” on page 215.• Some storage arrays make recommendations on queue depth and other settings. Typically, thesesettings are configured globally at the ESXi host level. Making a change for one array impacts otherarrays that present LUNs to the host. For information on changing queue depth, see the VMwareknowledge base article at http://kb.vmware.com/kb/1267.• Use single-initiator-single-target zoning when zoning ESXi hosts to Fibre Channel arrays. With this typeof configuration, fabric related events that occur on one array do not impact other arrays. For moreinformation about zoning, see “Using Zoning with Fibre Channel SANs,” on page 36.Making LUN DecisionsYou must plan how to set up storage for your ESXi systems before you format LUNs with VMFS datastores.When you make your LUN decision, keep in mind the following considerations:• Each LUN should have the correct RAID level and storage characteristic for the applications running invirtual machines that use the LUN.• Each LUN must contain only one VMFS datastore.• If multiple virtual machines access the same VMFS, use disk shares to prioritize virtual machines.You might want fewer, larger LUNs for the following reasons:• More flexibility to create virtual machines without asking the storage administrator for more space.• More flexibility for resizing virtual disks, doing snapshots, and so on.• Fewer VMFS datastores to manage.You might want more, smaller LUNs for the following reasons:• Less wasted storage space.• Different applications might need different RAID characteristics.• More flexibility, as the multipathing policy and disk shares are set per LUN.• Use of Microsoft Cluster Service requires that each cluster disk resource is in its own LUN.• Better performance because there is less contention for a single volume.When the storage characterization for a virtual machine is not available, there is often no simple method todetermine the number and size of LUNs to provision. You can experiment using either a predictive oradaptive scheme.VMware, Inc. 29