What is a Hybrid Flash Array?

A hybrid flash array, is a storage array that is comprised of both mechanical and solid state storage. Flash is used in place of traditional mechanical hard disk drives that are more commonly associated with RAID systems.

A storage array, also known as a disk array, is a storage system that stores data and can be file-based, block-based or object storage. Typically, the term ‘storage array’ is used to describe arrays with hard disk drives (HDDs), although increasingly, to meet the demand for higher performance, manufacturers are incorporating solid state drives (SSDs). There are some businesses that use all-flash arrays (AFAs). While initially built for storage area networks (SANs), there are now systems built that utilise flash memory instead. These arrays are designed to overcome the speed and performance limitations of traditional mechanical hard disk drives. A flash array can read data at speeds far exceeding one made up of hard disk drives and offers a substantial boost in performance.

Some manufacturers combine traditional HDD technology with flash storage, but are indicative of a vendor retrofitting an existing system with solid state storage; these are known as hybrid arrays. Flash memory is non-volatile, meaning it contains no moving parts. A flash array can transfer data at speeds far exceeding those of hard disk drives. Flash is a lot more expensive than the mechanical hard disk drive, but manufacturers have got around that with the development of multilevel cell (MLC) flash, which has significantly lowered the price of flash storage. While MLC flash is slower and less durable than single level cell (SLC) flash, software has been developed that increases the wear levelling, making MLC acceptable for enterprise level.

Hybrid flash arrays, as the name suggests, have an HDD and an SSD component, whereas all-flash arrays (AFAs) have purely solid state storage. The amount of flash storage in a hybrid array can vary – it can be a tiny amount, or a significant amount. By adding a small amount of flash to an existing purely mechanical array, the performance can be significantly increased, without the hefty cost. HDDs are cheaper, and offer a low cost per gigabyte. They do, however, have mechanical parts and are prone to failure, and use a lot of power; they’re also much slower. Conversely, flash, while more expensive per gigabyte, are much more reliable and faster. Concerns about limited storage capacity are disappearing as data reduction techniques, like data duplication and compression, are being utilised by businesses. Hybrid storage arrays are, essentially, the best of both worlds. They offer the low cost per gigabyte that is associated with the hard disk drive component, and a slight increase on performance, depending on how much flash storage is utilised.
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