Online SNIA Dictionary

[Storage System] 

A spare to which power is applied, and which is not operating, but which is otherwise usable as a hot spare.

[Network] 

The splitting of light into a series of "colors" from a few (sparse WDM) to many with a narrow wavelength separation (dense WDM) for the purpose of carrying simultaneous traffic over the same physical fiber (9 micron usually).

Each "color" carries a separate data stream.

[Network]  [Windows] 

1. Acronym for Wave Division Multiplexing.

2. Acronym for Windows Driver Model.

[Storage System] 

A set of algorithms utilized by a flash controller to distribute writes and erases across the cells in a flash device.

Cells in flash devices have a limited ability to survive write cycles. The purpose of wear leveling is to delay cell wear out and prolong the useful life of the overall flash device.

[Fibre Channel] 

An address identifier used to access a service provided by a Fibre Channel fabric.

The service may be distributed in many elements throughout the Fibre Channel Fabric or it may be centralized in one or a few elements. A well-known address is not subject to zone restrictions (i.e., a well-known address is always accessible, irrespective of the current active zone set).

[SCSI] 

A group of physical links that attaches a wide port to another wide port.

[SCSI] 

Any form of SCSI using a 16-bit data path.

In a wide SCSI implementation, the data transfer rate in MBytes per second is twice the number of megatransfers per second because each transfer cycle transfers two bytes. See fast SCSI, Ultra SCSI, Ultra2 SCSI, Ultra3 SCSI.

[Windows] 

The Microsoft framework that supports CIM and WBEM; a set of Windows operating system facilities that enable operating system components to provide management information to management agents.

[Windows] 

Acronym for Windows Management Instrumentation.

[Computer System] 

A group of UNIX or Windows computer system users and/or computers, usually with a common mission or project, that is created for administrative simplicity.

[Computer System] 

Software used in the load generator to stimulate the product under test.

A Port_Name that is worldwide unique.

Storage System] Increase in the number of write operations by the device beyond the number of write operations requested by hosts.

Examples: In flash storage this may happen because of garbage collection. In filesystems this may happen because writes to data blocks generally also require writes to inode blocks.

See JEDEC JESD218A,2/11

[Computer System] 

A caching technique in which the completion of a write request is signaled as soon as the data is in cache, and actual writing to non-volatile media occurs at a later time.

Write-back cache includes an inherent risk that an application will take some action predicated on the write completion signal, and a system failure before the data is written to non-volatile media will cause media contents to be inconsistent with that subsequent action. For this reason, good write-back cache implementations include mechanisms to preserve cache contents across system failures (including power failures) and to flush the cache at system restart time. See write through cache.

[Storage System] 

A potential data corruption problem for parity RAID technology resulting from an array failure while application I/O is outstanding, followed by an unrelated member disk failure (some time after the array has been returned to service).

Data corruption can occur if member data and parity become inconsistent due to the array failure, resulting in a false regeneration when data from the failed member disk is subsequently requested by an application. Parity RAID implementations typically include mechanisms to eliminate the possibility of write holes.