The introduction of Serial Attached SCSI (SAS) as the most recent evolution of SCSI required redefining the related standard for enclosure management, called SCSI Enclosure Services . SES-2, or SCSI Enclosure Management 2 first revision, was introduced in 2002 and is now at revision 20. SES-2 SCSI Enclosure Services (SES) permit the management and sense the state of power supplies, cooling devices, LED displays, indicators, individual drives, and other non-SCSI elements installed in an enclosure. SES2 alerts users about drive, temperature and fan failures with an audible alarm and a fan failure LED.
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 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.
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.
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 SES-2 command set uses the SCSI SEND DIAGNOSTIC and RECEIVE DIAGNOSTIC RESULTS commands to obtain configuration information for the enclosure and to set and sense standard bits for each element installed in the enclosure. The SEND DIAGNOSTIC command is used to send control information to internal or external LED indicators or to instruct one enclosure element to change its state or perform an operation.
The application client has two mechanisms for accessing the enclosure service process:
The SES-2 process handles a single primary subenclosure or multiple subenclosures. In the second case, one primary subenclosure will manage all the other secondary subenclosures.
Like SES, SES-2 establishes two types of thresholds for elements with limited sensing capability, like voltage, temperature, current etcetera: critical and warning. So for example in the case of temperature we may have:
When managed values fall within the warning range, the SES-2 processor will communicate a warning signal to the application client, typically a Host Bus Adapter (HBA). When values fall outside acceptable ranges, depending from the commands supported by the device server, the sense code shall be HARDWARE FAILURE or ENCLOSURE FAILURE.
SES-2 lists four types of reporting methods:
If you are a member of the T10 working group, the Standard, controlled by the T10 technical committee, can be found at:
http://www.t10.org/cgi-bin/ac.pl?t=f&f=ses2r19a.pdf
Due to INCITS policy changes the SCSI T10 drafts for released standards are no longer available online for non-T10 members and must be purchased from INCITS at http://www.incits.org . See the official INCITS policy at http://www.incits.org/rd1/INCITS_RD1.pdf .
SES-2 over I²C is still used for storage backplanes enclosure management, although a competing method for enclosure management communication is now becoming prominent. Serial GPIO (SGPIO), provides a simpler, less expensive solution and is now more widespread than SES-2.
Serial General Purpose Input/Output (SGPIO) is a four-signal bus used between a host bus adapter (HBA) and a backplane. Of the four signals, three are driven by the HBA and one by the backplane. Typically, the HBA is a storage controller located inside a server, desktop, rack or workstation computer that interfaces with hard disk drives (HDDs) to store and retrieve data. It is considered an extension of the general-purpose input/output (GPIO) concept.
American Megatrends’ Backplane controllers, the MG9071 and MG9072 can used either SES-2 or SGPIO for enclosure management with a simple configuration selection.
A backplane is a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used as a backbone to connect several printed circuit boards together to make up a complete computer system. Backplanes commonly use a printed circuit board, but wire-wrapped backplanes have also been used in minicomputers and high-reliability applications.
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.
Serial ATA is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard to become the predominant interface for storage devices.
A disk array controller is a device which 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.
A disk enclosure is a specialized casing designed to hold and power disk drives while providing a mechanism to allow them to communicate to one or more separate computers.
In computer storage, a logical unit number, or LUN, is a number used to identify a logical unit, which is a device addressed by the SCSI protocol or Storage Area Network protocols which encapsulate SCSI, such as Fibre Channel or iSCSI.
SCSI target devices provide a number of SCSI diagnostic pages. These can be used by a Send Diagnostic command to tell a target device to run a specialised self-test. The Receive Diagnostic Results command is used where the results from the self-test operation are non-trivial.
SCSI Enclosure Services (SES) devices contains a number of elements, each of which is defined by a one byte SCSI element code. There are many different element codes defined to cover various devices as shown in the list below.
A SCSI connector is used to connect computer parts that use a system called SCSI to communicate with each other. Generally, two connectors, designated male and female, plug together to form a connection which allows two components, such as a computer and a disk drive, to communicate with each other. SCSI connectors can be electrical connectors or optical connectors. There have been a large variety of SCSI connectors in use at one time or another in the computer industry. Twenty-five years of evolution and three major revisions of the standards resulted in requirements for Parallel SCSI connectors that could handle an 8, 16 or 32 bit wide bus running at 5, 10 or 20 megatransfer/s, with conventional or differential signaling. Serial SCSI added another three transport types, each with one or more connector types. Manufacturers have frequently chosen connectors based on factors of size, cost, or convenience at the expense of compatibility.
Parallel SCSI is the earliest of the interface implementations in the SCSI family. SPI is a parallel data bus; There is one set of electrical connections stretching from one end of the SCSI bus to the other. A SCSI device attaches to the bus but does not interrupt it. Both ends of the bus must be terminated.
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:
SCSI standalone enclosure services is a computer protocol used mainly with disk storage enclosures. It allows a host computer to communicate with the enclosure to access its power, cooling, and other non-data characteristics.
In computer storage, SAF-TE is an industry standard to interface an enclosure to a (parallel) SCSI subsystem to gain access to information or control for various elements and parameters. These include temperature, fan status, slot status (populated/empty), door status, power supplies, alarms, and indicators. Practically, any given SAF-TE device will only support a subset of all possible sensors or controls.
The International Blinking Pattern Interpretation (IBPI) is an internal computer hardware standard. It defines two items:
SCSI / ATA Translation (SAT) is a set of standards developed by the T10 subcommittee, defining how to communicate with ATA devices through a SCSI application layer. The standard attempts to be consistent with the SCSI architectural model, the SCSI Primary Commands, and the SCSI Block Commands standards.
USB Attached SCSI (UAS) or USB Attached SCSI Protocol (UASP) is a computer protocol used to move data to and from USB storage devices such as hard drives (HDDs), solid-state drives (SSDs), and thumb drives. UAS depends on the USB protocol, and uses the standard SCSI command set. Use of UAS generally provides faster transfers compared to the older USB Mass Storage Bulk-Only Transport (BOT) drivers.
Old link : [broken] http://www.t10.org/ftp/t10/drafts/ses2/ses2r19a.pdf
New link : [restricted] http://www.t10.org/cgi-bin/ac.pl?t=f&f=ses2r19a.pdf
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