As a storage and virtualization expert, I have been working with various technologies that enable efficient data management and virtual machine operations. One of the key concepts in the realm of virtual machine storage is the Logical Unit Number, or LUN.

In VMware, a LUN is a logical representation of storage that is presented to the virtual environment. It is a way to abstract the physical storage from the virtual machines (VMs), allowing for a more flexible and manageable storage allocation. The concept of a LUN is not exclusive to VMware; it is a widely used term in the storage industry.

A LUN can be thought of as a container or a partition of storage that is carved out from a larger storage array. It can be as small as a few megabytes or as large as several terabytes, depending on the requirements. The size and configuration of a LUN are determined by the storage administrator based on the needs of the virtual machines that will use it.

The LUN can be backed by a single disk or it can span across multiple disks, depending on the desired performance, redundancy, and capacity. When a LUN is backed by multiple disks, it is typically configured in a RAID (Redundant Array of Independent Disks) setup to provide data protection and performance benefits.

In VMware, a LUN is connected to a host using a storage protocol such as Fibre Channel or iSCSI. Once connected, the host can then present the LUN to a virtual machine as a SCSI device, which the VM can use as its primary storage for its virtual disk file (VMDK). This allows the VM to interact with the storage as if it were a physical disk.

A datastore in VMware is a different concept from a LUN. A datastore is a repository of files that are used by virtual machines. It is essentially a storage container that holds the VMDK files, configuration files, and other virtual machine-related files. A datastore can be based on a LUN, but it is a higher-level abstraction that is managed by VMware vSphere.

The relationship between a LUN and a datastore can be summarized as follows: a LUN is a block of storage that is made available to the host, while a datastore is a VMware-managed file system that sits on top of that block storage. Multiple datastores can reside on a single LUN, and a single datastore can span multiple LUNs.

In terms of management, LUNs are typically managed by the storage administrator, who is responsible for configuring the LUNs, setting up RAID, and ensuring that the storage is available and performing well. On the other hand, datastores are managed within the VMware environment by the virtualization administrator, who allocates datastores to virtual machines and manages the files within them.

In conclusion, understanding the role of LUNs in VMware is crucial for effective storage management in a virtualized environment. They provide a flexible and efficient way to allocate storage resources to virtual machines, while datastores offer a convenient way to manage the files that make up those virtual machines.

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A LUN is a logical section of storage. A LUN can be backed by a single disk or multiple disks. It can also be allocated from a disk pool/volume/aggregate depending on the storage vendor's terminology. A datastore is a description VMware uses for an area of storage that virtual machines can reside on.Apr 9, 2013read more >>