Disk array

A disk array is a disk storage system which contains manifold disk drives. It is differentiated from a disk field, in that an array has cache memory and superior functionality, like RAID and virtualization.

Components of a characteristic disk array include:

* Disk array controllers
* Cache memories
* Disk enclosures
* Power supplies

Typically a disk array provides increased availability, resiliency and maintainability by using additional, redundant components (controllers, power supplies, fans, etc.), frequently up to the point at what time all single points of failure (SPOFs) are eliminated from the design. Additionally those mechanisms are often hot-swappable.

Typically, disk arrays are divided into five categories: NAS, Modular SAN arrays, Monolithic SAN arrays, Storage Virtualization and Utility SAN Arrays.

Solid-state drive

A solid-state drive (SSD) is a data storage device that uses solid-state memory to store constant data. Unlike flash-based memory cards and USB flash drives, a SSD emulates a hard disk drive interface, thus easily replacing it in the majority applications. An SSD using SRAM or DRAM (instead of flash memory) is frequently called a RAM-drive.

The unique usage of the term solid-state (from solid-state physics) refers to the employ of semiconductor devices quite than electron tubes, but has in this background been adopted to differentiate solid-state electronics from electromechanical devices as well. With no moving parts, solid-state drives are intrinsically less fragile than hard disks and so also silent (unless a cooling fan is used); as there are no mechanical delays, they typically enjoy low access time and latency.

SSDs have begun to appear in laptops, although they are at present considerably more expensive per unit of capacity than hard drives.

Firmware

Firmware is a special-purpose module of low-level software that serves two purposes. Initial, it acts like BIOS, enabling the device to get stock of its capabilities and to make those capabilities functional. Next, it coordinates the activities of the hardware throughout normal operation and contains programming constructs used to do those operations. For example, in a typical modem, the firmware will be a issue in establishing the modem's data rate, command set recognition, and particular feature completion.

Firmware is stored in a particular type of memory chip that doesn't misplace its storage capabilities when power is detached or lost. This non-volatile memory is classified as "read-only" memory (ROM) since the user, during usual operation, cannot modify the information stored there. The basic type of chip is called a PROM, which is programmable by some technician who has a programming console. An essential PROM receives one version of firmware. That code is "burned in" to the PROM and cannot be distorted. To update the firmware, the PROM must be actually removed from the device and replaced with a new chip.