2-1-5 Virtual Disks Explained

Key Concepts

• Virtual Disks
• Virtual Disk Types
• Storage Allocation
• Benefits of Virtual Disks

Virtual Disks

Virtual disks are software-based representations of physical storage devices within a virtualization environment. They allow virtual machines (VMs) to have their own independent storage, similar to how physical servers use hard drives. Virtual disks can be created, resized, and managed without affecting the underlying physical storage.

Virtual Disk Types

There are several types of virtual disks, including:

• Thin Provisioned: These disks allocate storage space on demand, meaning they only use the actual space required by the data. This allows for efficient use of storage resources but requires careful monitoring to avoid over-provisioning.
• Thick Provisioned: These disks allocate the full amount of storage space upfront. While they consume more storage initially, they offer better performance and are less prone to storage issues.
• Raw Device Mappings (RDM): These disks map directly to a physical storage device, bypassing the hypervisor's file system. RDMs are useful for applications that require direct access to storage, such as databases.

Storage Allocation

Storage allocation for virtual disks involves assigning physical storage resources to virtual disks. This can be done dynamically or statically, depending on the type of virtual disk and the needs of the VM. Proper storage allocation ensures that each VM has sufficient storage performance and capacity without overloading the physical storage infrastructure.

Benefits of Virtual Disks

The benefits of using virtual disks include:

• Flexibility: Virtual disks can be easily created, resized, and moved between VMs and physical storage devices, providing flexibility in storage management.
• Efficiency: Thin-provisioned disks allow for efficient use of storage resources, reducing waste and improving cost-effectiveness.
• Isolation: Each VM has its own virtual disk, ensuring that storage issues in one VM do not affect others.
• Scalability: Virtual disks can be scaled up or down as needed, accommodating changes in storage requirements without disrupting the VM.

Examples and Analogies

Think of virtual disks as digital bookshelves in a library. Just as each book (VM) has its own shelf (virtual disk), the library (hypervisor) manages the space and ensures that each book can be easily accessed and moved. The library can also optimize space by using smaller shelves (thin-provisioned disks) for books that don't take up much space.

Another analogy is a shared kitchen pantry. Just as each family member (VM) has their own designated shelf (virtual disk) for storing food, the pantry (hypervisor) ensures that everyone has enough space without overcrowding. The pantry can also be rearranged (resized) to accommodate changes in storage needs.