vVols User Guide: Terminology

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Both VMware and Pure Storage use many acronyms or abbreviations in either user guides, how-to's, quick start guides or deep dives. This article will give a quick overview of the common terminology used by both VMware and Pure Storage in the VMware vSphere Virtual Volumes ecosystem.

vVols Terminology

These are the core terms to know and understand when discussing vVols and the implementation with Pure Storage's FlashArray. Some aspects have more than one term that applies to them, both will be covered in the table.

Name/Concept	Explanation
Protocol Endpoint (PE)	A PE is a volume of zero capacity with a special setting in its Vital Product Data (VPD) page that ESXi detects during a SCSI inquiry. The PE effectively serves as a mount point for vVols. A PE is the only FlashArray volume that must be manually connected to hosts to use vVols. The industry term for a PE is "Administrative Logical Unit".
VASA	vSphere APIs for Storage Awareness (VASA) is the VMware-designed API used to communicate between vSphere and the underlying storage. For Pure Storage, this is the FlashArray.
SOAP	In the Days before REST API was more widely used, SOAP (Simple Object Access Protocol) was a messaging protocol that was used to exchange structured data (information) via web services (HTTP). SOAP uses an XML structure to exchange the information between source and destination. SOAP is heavily used in the management communication of the vSphere environment, vCenter Services and most important for the purpose of this KB, VASA.
Management Path or Control Path	This is the TCP/IP path between the compute management layer (vSphere) and the storage management layer (FlashArray). Requests such as creating, deleting and otherwise managing storage are issued on this path. This is done via HTTPS and TLS 1.2 over port 8084 for the FlashArray VASA Provider.
Data Path or Data Plane	The Data Path is the established connection from the ESXi hosts to the Protocol Endpoint on the FlashArray. The Data Path is the flow that SCSI Ops are sent and received, just as any traditional SAN. This connection is established over the storage fabric. Today this means iSCSI or Fibre Channel.
SPBM	Storage Policy Based Management (SPBM) is a framework designed by VMware to provision and/or manage storage. Users can create policies of selected capabilities or tags and assign them to a VM or specific virtual disk. SPBM for internal storage is called vSAN, SPBM for external storage is called vVols. A vendor must support VASA to enable SPBM for their storage.
VASA Provider Storage Provider	A VASA provider is an instance of the VASA service that a storage vendor offers a customer that is deployed in their environment. For the FlashArray, the VASA Providers are built into the FlashArray controllers and will be represented as VASA-CT0 and VASA-CT1. The term Storage Provider is used in vCenter to represent the VASA Providers for a given FlashArray.
Virtual Volume (vVol)	Virtual Volumes (vVols) is the name for this full architecture. A specific vVol is any volume on the array that is in use by the vSphere environment and managed by the VASA provider. A vVol based volume is not fundamentally different than any other volume on the FlashArray. The main distinction is that when it is in use, it is attached as a Sub-LUN via a PE, instead of via a direct LUN.
vVol Datastore vVol Storage Container	The vVol Datastore is not a LUN, file system or volume. A vVol Datastore is a target provisioning object that represents a FlashArray, a quota for capacity, and is a logical collection of config vVols. While the object created in vCenter is represented as a Datastore, the vVol Datastore is really a Storage Container that represents that given FlashArray.
SPS	This is a vCenter deamon called Storage Policy Service (SPS or vmware-sps). The SMS and SPBM services run as part of the Storage Policy Service.
SMS	A vCenter Service called Storage Management Service (SMS).
vvold	This is the service running on ESXi that handles the management requests directly from the ESXi host to the VASA provider as well as communicates with the vCenter SMS service to get the Storage Provider information.

vVols Replication Terminology

These terms are fundamental to how the APIs and integration with vVols replication will work.

Name/Concept	Explanation
Replication Provider	A VASA provider that supports VASA version 3 and array based replication-type features. This will inform VMware of replication features, configure VMs with replication, and inform VMware of compliance.
Storage Capabilities	The array based replication features offered up by a replication provider. These are very vendor specific. This can be replication interval, consistency groups, concurrency, retention, etc.
Storage Policy	A collection of VASA capabilities that are assembled together by a user and assigned values.
Fault Domain	This is an available target in the replication group. In other words, each fault domain is an array that you can fail VMs in that replication group over to. Fault domain = Array.
Source Replication Group	A unit of failover for replicated vVol VMs. Individual VM failover is not possible (unless it is the only VM in the replication group). Replicated vVols are put into a source group. Every source group has a respective target group on each replication target (fault domain). The source replication group will be associated to a FlashArray protection group on the source FlashArray. e.g. `pgroup-1`
Target Replication Group	For every fault domain specified in a source replication group, there is a target replication group. Test failovers, failovers, and reprotects are executed against a target replication group. If there is a DR event, it is possible that only the target group is left. It is designed to withstand the failure of the source. The target replication group will be associated to a target protection group on the target FlashArray. e.g. `FlashArray-A:pgroup-1`

With these terms covered, here is a visual representation of what these terms correlate to. In the illustration below there are three FlashArrays, with FlashArray-A replicating to FlashArray-B and FlashArray-C.

VMware's vSphere user guide covers vVols replication groups and fault domains in some additional detail. Please refer to that user guide if additional context is desired.