FibreChannel Interface ANSI developed the FC Standard in 1988 as a practical
and expandable method of using fiber optic cabling to transfer data among desktop
computers, workstations, mainframes, supercomputers, storage devices, and display
devices. ANSI later changed the standard to support copper cabling; today, some
kinds of FC use two-pair copper wire to connect the outer four pins of a nine-pin
type connector.
Fibre Channel over Ethernet Interface Fibre Channel over Ethernet (FCoE)
is a computer network technology that encapsulates Fibre Channel frames over Ethernet
networks. This allows Fibre Channel to use Ethernet networks while preserving the
Fibre Channel protocol. The specification was part of the International Committee
for Information Technology Standards T11 FC-BB-5 standard published in 2009. FCoE
maps Fibre Channel directly over Ethernet while being independent of the Ethernet
forwarding scheme. The FCoE protocol specification replaces the FC0 and FC1 layers
of the Fibre Channel stack with Ethernet. By retaining the native Fibre Channel
constructs, FCoE is meant to integrate with existing Fibre Channel networks and
management software. FCoE operates directly above Ethernet in the network protocol
stack, in contrast to iSCSI which runs on top of TCP and IP. As a consequence, FCoE
is not routable at the IP layer, and will not work across routed IP networks. Since
classical Ethernet had no priority-based flow control, unlike Fibre Channel, FCoE
required enhancements to the Ethernet standard to support a priority-based flow
control mechanism (to reduce frame loss from congestion). The IEEE standards body
added priorities in the data center bridging Task Group.
iSCSI Interface iSCSI is an acronym for Internet Small Computer System Interface,
an Internet Protocol (IP)-based storage networking standard for linking data storage
facilities. By carrying SCSI commands over IP networks, iSCSI is used to facilitate
data transfers over intranets and to manage storage over long distances. iSCSI 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.
The protocol allows clients (called initiators) to send SCSI commands (CDBs) to
SCSI storage devices (targets) on remote servers. It is a storage area network (SAN)
protocol, allowing organizations to consolidate storage into data center storage
arrays while providing hosts (such as database and web servers) with the illusion
of locally attached disks. Unlike Fibre Channel, which requires special-purpose
cabling, iSCSI can be run over long distances using existing network infrastructure.
iSCSI was submitted as draft standard in March 2000
Multi-Path I/O Microsoft MPIO architecture supports iSCSI, Fibre Channel
and serial attached storage (SAS) SAN connectivity by establishing multiple sessions
or connections to the storage array. Multi-pathing solutions use redundant physical
path components - adapters, cables, and switches - to create logical paths between
the server and the storage device. In the event that one or more of these components
fails, causing the path to fail, multi-pathing logic uses an alternate path for
I/O so that applications can still access their data. Each network interface card
(in the iSCSI case) or HBA should be connected by using redundant switch infrastructures
to provide continued access to storage in the event of a failure in a storage fabric
component.
Offloaded Data Transfer (ODX) Microsoft-developed data transfer technology
- offloaded data transfer (ODX). Instead of using buffered read and buffered write
operations, Windows ODX starts the copy operation with an offload read and retrieves
a token representing the data from the storage device, then uses an offload write
command with the token to request data movement from the source disk to the destination
disk. The copy manager of the storage devices performs the data movement according
to the token. Note that this feature will only work on storage devices with SPC4
and SBC3 specification implementation.
RAID RAID (redundant array of independent disks) is a storage technology
that combines multiple disk drive components into a logical unit for the purposes
of data redundancy and performance improvement. Data is distributed across the drives
in one of several ways, referred to as RAID levels, depending on the specific level
of redundancy and performance required. Windows Server Certification Requirements
specify that RAID controllers and RAID arrays must support, at a minimum, one of:
RAID1, RAID 5, RAID6 or RAID 1/0, with RAID levels greater than RAID 0 providing
protection against unrecoverable (sector) read errors, as well as whole disk failures.
SAS Interface Serial Attached SCSI (SAS) is a point-to-point serial protocol
that moves data to and from computer storage devices such as hard drives and tape
drives. SAS replaces the older Parallel SCSI (Small Computer System Interface),
bus technology that first appeared in the mid-1980s. SAS uses the standard SCSI
command set. The T10 technical committee of the International Committee for Information
Technology Standards (INCITS) develops and maintains the SAS protocol; the SCSI
Trade Association (SCSITA) promotes the technology. A typical Serial Attached SCSI
system consists of the following basic components:
An Initiator: a device that originates device-service and task-management requests
for processing by a target device and receives responses for the same requests from
other target devices. Initiators may be provided as an on-board component on the
motherboard (as is the case with many server-oriented motherboards) or as an add-on
host bus adapter.
A Target: a device containing logical units and target ports that receives device
service and task management requests for processing and sends responses for the
same requests to initiator devices. A target device could be a hard disk or a disk
array system.
A Service Delivery Subsystem: the part of an I/O system that transmits information
between an initiator and a target. Typically cables connecting an initiator and
target with or without expanders and backplanes constitute a service delivery subsystem.
Expanders: devices that form part of a service delivery subsystem and facilitate
communication between SAS devices. Expanders facilitate the connection of multiple
SAS End devices to a single initiator port.
The SAS bus operates point-to-point while the SCSI bus is "multi-drop" (electrically
parallel), reducing contention. SAS has no termination issues and does not require
terminator packs like parallel SCSI. SAS eliminates clock skew. SAS allows up to
65,535 devices through the use of expanders, while Parallel SCSI has a limit of
8 or 16 devices on a single channel. SAS allows a higher transfer speeds than most
parallel SCSI standards. SAS devices feature dual ports, allowing for redundant
backplanes/multipath I/O
SATA Interface Serial ATA (SATA) is a computer bus interface that connects
host bus adapters to mass storage devices such as hard disk drives and optical drives.
Serial ATA replaces Parallel ATA or PATA, offering several advantages over the older
interface: reduced cable size and cost (seven conductors instead of 40), native
hot swapping, faster data transfer through higher signaling rates, and more efficient
transfer through an (optional) I/O queuing protocol. SATA host adapters and devices
communicate via a high-speed serial cable over two pairs of conductors. To ensure
backward compatibility with legacy ATA software and applications, SATA uses the
same basic ATA and ATAPI command-set as legacy ATA devices.
SCSI Interface Small Computer System Interface (SCSI) is a set of standards
for physically connecting and transferring data between computers and peripheral
devices. The SCSI standards define commands, protocols and electrical and optical
interfaces. SCSI is most commonly used for hard disks 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.
Thin Provisioning (TP) Thin provisioning is the act of using virtualization
technology to give the appearance of having more physical resources than are actually
available, on a just-enough and just-in-time basis.. If a system always has enough
resource to simultaneously support all of the virtualized resources, then it is
not thin provisioned. The efficiency of thin or thick/fat provisioning is a function
of the use case, not the technology. Thick provisioning is typically more efficient
when the amount of resource used is very close to the amount of resource allocated.
Thin provisioning is more efficient where the amount of resource used is much smaller
than allocated so that the benefit of providing only the resource needed exceeds
the cost of the virtualization technology used. Just in time allocation is not the
same as thin provisioning. Most file systems back files just in time but are not
thin provisioned. Over-allocation is not the same as thin provisioning; resources
can be over-allocated / oversubscribed without using virtualization technology.