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What is a Virtual Storage?

What is a Virtual Storage?


Physical storage:

  • Local storage: Directly attached storage that will be used as data store (VMFS: block-based local storage)

SAS/ SATA/ SSD drives directly attached to the server

  • Shared storage

Fibre Channel SAN storage

Fibre Channel over Ethernet

iSCSI storage

NFS (Network File System) this is a linux-based file system that is implemented on NAS storage devices. NFS is Similar to the SMB sharing in windows. NFS is file level vs Block level.


Vmware has the capability to use the network shared storage. This feature gives the administrators the ability to use the network (Shared storage) for the HV (High availability of virtual machines); disaster recovery and vmotion capabilities.


– NFS, DAS and Virtual SAN cannot be used to boot the system from the network but the Fibre Channel, FCoE and ISCSi add the capability of booting from SAN for the virtual machines.


What is a Datastore in VMware world?

Datastore is a logical storage used by VMware that can be used to store Virtual Machine files, Templates and ISO images. A Datastore can be the allocated space on physical devices directly attached to the server or the network storage space provided by SAN devices.

What is VMFS?

VMware Virtual Machine File System is a high performance cluster file system that increases resource utilization by providing multiple virtual machines with concurrent access to a consolidated pool of clustered storage. VMFS provides the foundation for virtualization spanning multiple servers, enabling services such as VMware Vmotion, Distributed Resource Scheduler and VMware High Availability.

VMFS is optimized for Virtual machines in a clustered environment. It has the capability of dynamically expanding by spanning multiple storage resources.With VMFS all hosts can access one Datastore at the same time. the cluster feature prevents the data corruption during concurrent access.

With VMFS the data storage is optimized with the 1MB block size that is good for storing large files. On the other hand the subblock addressing optimizes the storing of small files. Subblock size is 8 KB.

Block-level locking prevents the data corruption on the disk as it locks that block that is being used by one Virtual machine and does not allow the block of the data to be used by another device at the same time.

Virtual SAN:

Virtual SAN is a combined space on different VMware ESXi servers that create a shared Datastore. The Virtual SAN can consist of SSD and/or mechanical disks.

This Virual SAN can be Hybrid or All-Flash. In Hybrid distributed Virtual SAN the SSD (Flash) can be used for cashing and the magnetic disks will be used to store data. In All-Flash system; the caching and data store will both happen on the SSD drives.