How exactly does virtualization save companies money

Overview of virtualization concepts

With storage virtualization (Storage virtualization) is a virtualization concept that aims to map various storage resources of a company such as hard disk drives, flash memory or tape drives virtually and as coherent ones Storage pool provide. A virtualization solution establishes an abstraction layer between the various physical storage media and the logical level on which they are combined Centrally manage storage resources using software to let.

Virtual memory can also be broken down into quotas and allocated to selected applications. Despite virtualization, users can always access stored data via the same file paths, even if the physical storage location changes. This is ensured by an assignment table managed by the virtualization software. One speaks of one Mapping the physical storage media on a logical drive (also Volumes called).

Logical drives are not tied to the physical capacity limits of the underlying individual storage media. Storage virtualization therefore offers significantly more Flexibility in the allocation of storage resources. The hardware available for data storage can be used more effectively. For companies, this means that storage capacities in the data center can be provided more cost-effectively.

Storage virtualization is usually used in a corporate context block based implemented. With block storage, data is divided into blocks of equal size. Each data block is given a unique address. This is done by the virtualization software in the central assignment table (Mapping table) saved. The assignment table thus contains all metadata that are required to locate the physical storage location of a data block. This mapping makes it possible to manage data on the virtual level independently of the respective controller of the physical storage medium and thus to move, copy, mirror or replicate, for example.

In practice, block-based virtualization can be implemented using three different approaches:

  • Host based
  • Device based
  • Network based

Host-based storage virtualization

Host-based virtualization of storage resources is an approach to storage virtualization that is typically used in combination with virtual machines is used. With this concept, a host system presents one or more guest systems (see Hardware virtualization) virtual drives on an abstraction level, which is either created by an internal operating system Volume manager or separate software (a so-called storage hypervisor) is implemented. The hardware (hard drives and other storage media) are accessed by the device drivers of the host system. The volume manager resp. Storage hypervisor is used as a software layer above the device driver and manages input and output (I / O for short), I / O mapping tables and the metadata search.

Native functions that make it possible to create virtual drives are available in almost all modern operating systems.

  • Windows: Logical Disk Manager (LDM)
  • macOS: CoreStorage (since OS X Lion)
  • Linux: Logical Volume Manager (LVM)
  • Solaris and FreeBSD: zPools of the Z File Systems (ZFS) file system

The host-based storage virtualization works without additional hardware, supports any storage device and can be implemented with little effort. In addition, the approach offers the best performance compared to other concepts, since each storage device is immediate and therefore without latency is addressed. However, users have to accept that storage virtualization - and with it the possibility of optimizing storage utilization - is limited to the respective host.

Device-based storage virtualization

Also Disk arrays - Mass storage devices with which hard disks can be made available in the network - offer the possibility of virtualizing storage resources. So-called RAID schemes for use. With RAID (short for: Redundant Array of Independent Disks, the redundant arrangement of independent hard disks) is a concept of data storage in which several physical drives are combined into a virtual storage platform. The aim of storage virtualization is fail-safe through redundancy. For this purpose, the data is mirrored in a disk array and distributed on different hard disks.