The principle of the magnetic storage medium was born in the 1950s by the US company IBM. Since the hard disk conquered the mass market in the 1980s, the capacity of hard disk drives has grown rapidly: In the meantime, there are individual consumer HDDs that can score with a capacity of up to 20 terabytes. SSDs have even cracked the 100 terabyte mark. Over the years, various interfaces have also been developed that can be used to connect a mass storage device to the computing unit:
SATA hard disks
The abbreviation SATA stands for "Serial Advanced Technology Attachment". An essential difference to other interfaces is that with SATA hard disks the stored data is transmitted serially - i.e. bit by bit. At the beginning of the 2000s, this technology became more and more popular for home use because, in contrast to the conventional IDE hard disk, a significantly faster data transfer became possible. With the further development "SATA Express", data rates of up to just under 2,000 megabytes per second are feasible today. Other SATA connection variants include External Serial ATA (eSATA) for connecting external hard disks as well as mini SATA (mSATA) and micro SATA for space-saving and smaller hard disks in notebooks, netbooks and ultrabooks.
In a RAID (Redundant Array of Independent Disk) system, several server hard disks can be configured to form a single logical drive in the array. In server operation, these storage arrays are used, for example, to store redundant information from which the stored data can be rebuilt in the event of a technical failure.
To set up a RAID system, at least two hard disks are always necessary. In addition to increased data security, RAID systems also offer the advantage that hard disks can be easily replaced during server operation. This means that customers do not have to put up with temporary hardware failures. Another advantage is that the data transfer rate in a hard disk network can be faster than with individual hard disks if the system is configured accordingly.
Basically, there are two ways to design a RAID system: In a hardware RAID, the interaction of the hard disks is managed by a RAID controller that is connected to the motherboard. If, on the other hand, the interaction of several hard disks in a network is monitored and controlled by a computer programme, IT experts speak of a software RAID.
Serial Attached SCSI (SAS)
Serial Attached SCSI (SAS) is another interface for connecting hard disks. The technology inherited the parallel SCSI interface at the beginning of the new millennium and offered significantly better data throughput rates. Another advantage of SAS is that a single storage domain can be built up from a large number of SAS hard disks via edge or fanout expanders. Theoretically, it is possible to network a five-digit number of hard disks via Serial Attached SCSI.
Network-attached storage (NAS) makes it very easy to provide independent storage space in a computer network. This means that the storage space can be accessed by several computers regardless of location. NAS systems are often connected to the client computers via a local area network (LAN). Thanks to modern network technology, solutions via WLAN are also becoming more widespread. Network Attached Storage is thus a classic server service. Thanks to almost unlimited scalability, you can adapt your storage space individually to your current needs; upgrades and downgrades are possible at any time.
Fibre Channel is one of the most modern solutions for hard disk interfaces. Storage Area Networks equipped with this system offer high-performance data transfer, enabling transfers of over three gigabytes per second in full duplex operation. Ethernet offers a similar technology, iSCSI (Internet Small Computer System Interface), which is often used for complex networks. However, due to a slightly increased load on the central processing unit (CPU), iSCSI systems do not work as economically as solutions with Fibre Channel.
Even though commercially available desktop hard disks are very powerful and durable, these hard disks are only suitable for use in servers to a limited extent. One of the reasons for this is that server hard disks have been specifically optimised for continuous operation by means of adapted firmware and a more robust design. There are also differences in the common sizes between a hard disk for servers and hard disks for exclusively private use.