VxRail Appliances are powered by VMware vSAN for enterprise-class software-defined storage. vSAN aggregates the locally attached disks of hosts in a vSphere cluster to create a pool of distributed shared storage. Capacity is scaled up by adding additional disks to the cluster and scaled out by adding additional VxRail nodes. vSAN is fully integrated with vSphere, and it works seamlessly with other vSphere features.
vSAN is notable for its efficiency and performance. vSAN is self-optimizing and balances allocation based on workload, utilization, and resource availability. vSAN delivers high performance, flash-optimized, HCI suitable for a variety of workloads. Enterprise-class storage features include:
With vSAN, disks on each VxRail node are automatically organized into disk groups with a single cache Drive and one or more capacity drives. These disk groups are used to form a single vSAN Datastore, which is accessible across all the nodes in a VxRail cluster.
VxRail provides two different vSAN node-storage configuration options: a hybrid configuration that uses both flash SSDs and mechanical HDDs, and an all-flash SSD configuration. The hybrid configuration uses flash SSDs for caching and mechanical HDDs for capacity and persistent data storage. The all-flash configuration uses flash SSDs for both caching and capacity. The following figure illustrates the basic concepts of vSAN:
Figure 8. The basic concepts of vSAN
vSAN is configured when the VxRail cluster is first initialized and is managed through vCenter. During the VxRail Appliance initialization process, vSAN creates a distributed shared datastore from the locally attached disks on each ESXi node. The amount of storage in the datastore is an aggregate of all the capacity drives in the cluster. The amount of usable storage will be dependent on the protection level used. The orchestrated vSAN configuration and verification performed as part of system initialization ensures consistent and predictable performance and a system configuration that follows best practices.
vSAN is policy-driven and designed to simplify storage provisioning and management. vSAN storage policies are based on rule sets that define storage requirements for VMs. Administrators can dynamically change a VM storage policy as requirements change. Examples of SPBM rules are the number of faults to tolerate, the data protection technique to use, and whether storage-level checksums are enabled.