What you should know about vSphere storage?
Local and Networked storage – local storage, named as DAS (direct attached disks) is directly attach to the host, but as design you have a limit of slots. Usually on VMware infrastructure the networked storage can be different types, but most importantly, can be shared and accessed by multiple hosts simultaneously. VMware supports virtualized shared storage, such as vSAN. vSAN transforms internal storage resources of your ESXi hosts into shared storage.
Fibre Channel (FC) storage – FC SAN is a specialized high-speed network that connects your hosts to high-performance storage devices. The network uses Fibre Channel protocol to transport SCSI traffic from virtual machines to the FC SAN devices. The FC connection is made via HBAs(Host Bus Adapters) adapters.
Internet SCSI (iSCSI) storage – Stores virtual machine files on remote iSCSI storage devices. iSCSI packages SCSI storage traffic into the TCP/IP protocol, so that it can travel through standard TCP/IP networks instead of the specialized FC network. With an iSCSI connection, your host serves as the initiator that communicates with a target, located in remote iSCSI storage systems.
Storage Device or LUN – the terms device and LUN are used interchangeably. Typically, both terms mean a storage volume that is presented to the host from a block storage system and is available for formatting.
ESXi offers the following types of iSCSI connections:
- Hardware iSCSI – Your host connects to storage through a third-party adapter capable of offloading the iSCSI and network processing. Hardware adapters can be dependent and independent.
- Software iSCSI – Your host uses a software-based iSCSI initiator in the VMkernel to connect to storage. With this type of iSCSI connection, your host needs only a standard network adapter for network connectivity. You must configure iSCSI initiators for the host to access and display iSCSI storage devices.
- Shared Serial Attached SCSI (SAS) – Stores virtual machines on direct-attached SAS storage systems that offer shared access to multiple hosts. This type of access permits multiple hosts to access the same VMFS (Virtual Machine File System) datastore on a LUN.
Few more types of storage types and
- VMware FileSystem (VMFS) datastores – is a cluster file system that facilitates storage virtualization for multiple installations of VMware ESX Server, a hypervisor that partitions physical servers into multiple virtual machines.
- Network FileSystem (NFS) datastores: This is for NAS storage
- VVol: introduced in vSphere 6.0 and is a new paradigm to access SAN and NAS storage in a common way and by better integrating and consuming storage array capabilities. With Virtual Volumes, an individual virtual machine, not the datastore, becomes a unit of storage management. And storage hardware gains complete control over virtual disk content, layout, and management.
- vSAN datastore: If you are using vSAN solution, all your local storage devices could be polled together in a single shared vSAN datastore. vSAN is a distributed layer of software that runs natively as a part of the hypervisor.
- Raw device Mapping – RDM is useful when a guest OS inside a VM requires direct access to a storage device.
VAAI – vSphere API for Array Integration – those APIs include several components. There are Hardware Acceleration APIs which help arrays to integrate with vsphere for offloading certain storage operations to an array. This reduces CPU overhead on a host.
vSphere API for Multipathing – This is known as Pluggable Storage Architecture (PSA), uses APIs which allows storage partners to create and deliver multipathing and load-balancing plugins which are optimized for each array. Plugins talk to storage arrays and chose the best path selection strategy to increase IO performance and reliability.