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

Chapter 19 Working with Virtual SANVirtual SAN provisions and manages each object individually creating a RAID configuration over thenetwork for every object. When creating an object for a virtual disk and determining how to distribute theobject in the cluster, Virtual SAN considers the following parameters:• Virtual disk requirements specified by the administrator in a form of a virtual machine storage policy.• Cluster resources and their utilization at the time of provisioning.For example, based on the availability policy, Virtual SAN determines how many replicas to create. Whilethe performance policy determines the amount of SSD allocated for caching for each replica and how manystripes to create for each replica.As the Virtual SAN cluster and the workloads evolve over time, Virtual SAN monitors the compliance of thevirtual disk with its policies and makes necessary adjustments to bring the object back to compliance or tooptimize the utilization of the cluster resources. Virtual SAN actively throttles the storage and networkthroughput used for reconfiguration to minimize the impact of reconfiguration to normal workloadexecution.Characteristics of Virtual SANThis topic summarises characteristics that apply to Virtual SAN, as well as its clusters and datastores.When you work with Virtual SAN, consider the following :• Virtual SAN is implemented directly in the ESXi hypervisor.• Virtual SAN supports VMware features that require shared storage, such as HA, vMotion, and DRS.For example, if a host becomes overloaded, DRS can migrate virtual machines to other hosts in thecluster.• Virtual SAN integrates with vSphere data management features traditionally used with VMFS and NFSstorage. These features include snapshots, linked clones, vSphere Replication, and vSphere APIs forData Protection.• Virtual SAN works with Virtual Machine Storage Policies to support a virtual machine-centric storageapproach.Limitations of Virtual SAN• Virtual SAN does not support multiple Virtual SAN clusters for each host.• Virtual SAN does not support virtual machines with large capacity virtual disks, or disks greater than2TB.• You cannot use shared storage with Virtual SAN.• Virtual SAN supports only SATA and SAS storage. You cannot use storage attached through USB, FibreChannel, or iSCSI.• Virtual SAN does not support such features as Fault Tolerance, vSphere DPM, and Storage I/O Control.• Virtual SAN does not support native snapshots and SE Sparse disks.• Virtual SAN does not support SCSI reservations.Characteristics of a Virtual SAN Cluster• Virtual SAN clusters can include hosts with storage disks, or without. The minimum requirement isthree hosts with storage disks.• If a host contributes storage devices, it must have at least one SSD and one HDD device.• Only local or direct-attached storage devices can participate in a Virtual SAN cluster. Virtual SAN doesnot use any other storage, such as SAN or NAS, attached to cluster.VMware, Inc. 175