Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interfaces. SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.
In computing, iSCSI is an acronym for Internet Small Computer Systems Interface, an Internet Protocol (IP)-based storage networking standard for linking data storage facilities. It provides block-level access to storage devices by carrying SCSI commands over a TCP/IP network. iSCSI is used to facilitate data transfers over intranets and to manage storage over long distances. It can be used to transmit data over local area networks (LANs), wide area networks (WANs), or the Internet and can enable location-independent data storage and retrieval.
Disk formatting is the process of preparing a data storage device such as a hard disk drive, solid-state drive, floppy disk or USB flash drive for initial use. In some cases, the formatting operation may also create one or more new file systems. The first part of the formatting process that performs basic medium preparation is often referred to as "low-level formatting". Partitioning is the common term for the second part of the process, making the data storage device visible to an operating system. The third part of the process, usually termed "high-level formatting" most often refers to the process of generating a new file system. In some operating systems all or parts of these three processes can be combined or repeated at different levels and the term "format" is understood to mean an operation in which a new disk medium is fully prepared to store files. Some formatting utilities allow distinguishing between a quick format, which does not erase all existing data and a long option that does erase all existing data.
In computer hardware, a host controller, host adapter, or host bus adapter (HBA) connects a computer, which acts as the host system, to other network and storage devices. The terms are primarily used to refer to devices for connecting SCSI, Fibre Channel and SATA devices. Devices for connecting to IDE, Ethernet, FireWire, USB and other systems may also be called host adapters.
Logical block addressing (LBA) is a common scheme used for specifying the location of blocks of data stored on computer storage devices, generally secondary storage systems such as hard disk drives. LBA is a particularly simple linear addressing scheme; blocks are located by an integer index, with the first block being LBA 0, the second LBA 1, and so on.
A disk array controller is a device that manages the physical disk drives and presents them to the computer as logical units. It almost always implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additional disk cache.
In computing, Serial Attached SCSI (SAS) is a point-to-point serial protocol that moves data to and from computer-storage devices such as hard disk drives and tape drives. SAS replaces the older Parallel SCSI bus technology that first appeared in the mid-1980s. SAS, like its predecessor, uses the standard SCSI command set. SAS offers optional compatibility with Serial ATA (SATA), versions 2 and later. This allows the connection of SATA drives to most SAS backplanes or controllers. The reverse, connecting SAS drives to SATA backplanes, is not possible.
In computer data storage, a SCSI initiator is the endpoint that initiates a SCSI session, that is, sends a SCSI command. The initiator usually does not provide any Logical Unit Numbers (LUNs).
ATA over Ethernet (AoE) is a network protocol developed by the Brantley Coile Company, designed for simple, high-performance access of block storage devices over Ethernet networks. It is used to build storage area networks (SANs) with low-cost, standard technologies.
A NetApp FAS is a computer storage product by NetApp running the ONTAP operating system; the terms ONTAP, AFF, ASA, FAS are often used as synonyms. "Filer" is also used as a synonym although this is not an official name. There are three types of FAS systems: Hybrid, All-Flash, and All SAN Array:
- NetApp proprietary custom-build hardware appliances with HDD or SSD drives called hybrid Fabric-Attached Storage
- NetApp proprietary custom-build hardware appliances with only SSD drives and optimized ONTAP for low latency called ALL-Flash FAS
- All SAN Array build ontop of AFF platform, and provide only SAN-based data protocol connectivity.
In SCSI computer storage, computers and storage devices use a client-server model of communication. The computer is a client which requests the storage device to perform a service, e.g., to read or write data. The SCSI command architecture was originally defined for parallel SCSI buses but has been carried forward with minimal change for use with Fibre Channel, iSCSI, Serial Attached SCSI, and other transport layers.
The IBM SAN Volume Controller (SVC) is a block storage virtualization appliance that belongs to the IBM System Storage product family. SVC implements an indirection, or "virtualization", layer in a Fibre Channel storage area network (SAN).
Most recent SCSI enclosure products support a protocol called SCSI Enclosure Services (SES). The initiator can communicate with the enclosure using a specialized set of SCSI commands to access power, cooling, and other non-data characteristics.
The Enclosure Services Interface (ESI) is a computer protocol used in SCSI enclosures. This is part of a chain of connections that allows a host computer to communicate with the enclosure to access its power, cooling, and other non-data characteristics. This overall approach is called SCSI attached enclosure services:
In computer science, storage virtualization is "the process of presenting a logical view of the physical storage resources to" a host computer system, "treating all storage media in the enterprise as a single pool of storage."
The SCSI architectural model provides an abstract view of the way that SCSI devices communicate. It is intended to show how the different SCSI standards are inter-related. The main concepts and terminology of the SCSI architectural model are:
A logical disk, logical volume or virtual disk is a virtual device that provides an area of usable storage capacity on one or more physical disk drive(s) in a computer system. The disk is described as logical or virtual because it does not actually exist as a single physical entity in its own right. The goal of the logical disk is to provide computer software with what seems a contiguous storage area, sparing them the burden of dealing with the intricacies of storing files on multiple physical units. Most modern operating systems provide some form of logical volume management.
A storage area network (SAN) or storage network is a computer network which provides access to consolidated, block-level data storage. SANs are primarily used to access storage devices, such as disk arrays and tape libraries from servers so that the devices appear to the operating system as direct-attached storage. A SAN typically is a dedicated network of storage devices not accessible through the local area network (LAN).
In computing, Linux-IO (LIO) Target is an open-source implementation of the SCSI target that has become the standard one included in the Linux kernel. Internally, LIO does not initiate sessions, but instead provides one or more Logical Unit Numbers (LUNs), waits for SCSI commands from a SCSI initiator, and performs required input/output data transfers. LIO supports common storage fabrics, including FCoE, Fibre Channel, IEEE 1394, iSCSI, iSCSI Extensions for RDMA (iSER), SCSI RDMA Protocol (SRP) and USB. It is included in most Linux distributions; native support for LIO in QEMU/KVM, libvirt, and OpenStack makes LIO also a storage option for cloud deployments.
ONTAP or Data ONTAP or Clustered Data ONTAP (cDOT) or Data ONTAP 7-Mode is NetApp's proprietary operating system used in storage disk arrays such as NetApp FAS and AFF, ONTAP Select and Cloud Volumes ONTAP. With the release of version 9.0, NetApp decided to simplify the Data ONTAP name and removed word "Data" from it and remove 7-Mode image, therefore, ONTAP 9 is successor from Clustered Data ONTAP 8.
