vSphere Virtual Storage

Virtualized storage is an integral part of a VMware vSphere virtualization environment. vSphere storage virtualization is a combination of vSphere features and APIs that provide an abstraction layer for physical storage resources to be addressed, managed and optimized in a virtualization deployment.

Storage virtualization technology provides a fundamentally better way to manage storage resources for your virtual infrastructure, giving your organization the ability to:

• Significantly improve storage resource utilization and flexibility
• Simplify OS patching and driver requirements regardless of storage topology
• Increase application uptime and simplify day to day operations
• Leverage and complement your existing storage infrastructure

In a non-virtualized environment, servers connect directly to storage. Storage may be internal to the server chassis or in an external array. The biggest downside to storage in a non-virtualized environment is that a specific server expects complete ownership of the physical device, with an entire disk drive (or LUN in case of drive arrays) tied to a single server. Sharing storage resources in a non-virtualized environment requires complex cluster file systems or moving away from block-based storage to file based NAS (Network Attached Storage). Directly accessing block-based storage also presents complexity in terms of drivers, firmware and patches.

A virtual machine is stored as a set of files in its own directory in a datastore. Datastores are logical containers, analogous to file systems, which hide specifics of each storage device and provide a uniform model for storing virtual machine files. Datastores can also be used for storing ISO images, virtual machine templates and floppy images.

Depending on the type of storage used, datastores can be backed by the following file system formats:

VMFS allows multiple of VMware vSphere servers to access shared virtual machine storage concurrently. It also enables virtualization-based distributed infrastructure services such as vSphere DRS, vSphere HA, vSphere vMotion and vSphere Storage vMotion to operate across a cluster of vSphere servers. VMFS provides the foundation that enables the scaling of virtualization beyond the boundaries of a single system.

vSphere supports all common storage interconnects for block based storage, including:

• Direct-attached storage - Internal or external storage disks or arrays attached to the host through a direct connection instead of a network connection (usually SATA, IDE, EIDE, etc.)
• Fibre Channel - A high-speed fiber optic based transport protocol used for storage area networks (SANs). Fibre Channel encapsulates SCSI commands on the FC protocol.
• FCoE - Fibre Channel Over Ethernet. Fibre Channel traffic is encapsulated into Ethernet frames.
• iSCSI - iSCSI carries SCSI commands over IP networks

vSphere also supports placing datastores on NAS storage, accessed via an IP network.

vSphere greatly simplifies accessing storage from the guest operating system. The virtual hardware presented to a vSphere guest operating system includes a set of common SCSI and IDE controllers that have drivers available in nearly every operating system. The guest operating system sees a simple physical disk attached via a standard controller. Presenting a virtualized view of storage to the guest OS has a number of advantages, including:

• Easier Management. There is no need to maintain guest OS drivers for every type of controller available in your physical servers.
• Expanded Support and Access. Different types of storage interconnect, such as iSCSI and FCoE can be accessed by guest operating systems that would not natively support these protocols
• Improved Efficiency. Multipathing is provided at the vSphere Server level, rather than requiring redundant links and software configuration across a much larger number of physical servers