FlashCopy
Encyclopedia
FlashCopy is an IBM
feature supported on various IBM storage devices that makes it possible to create, nearly instantaneously, Point in Time copies of entire logical volumes or data sets. The Hitachi Data Systems
implementation providing similar function is branded as ShadowImage. Using either implementation, the copies are immediately available for both read and write access.
Version 1 of FlashCopy had limitations however. Although the copy or “flash” of a volume occurred instantaneously, the FlashCopy commands were issued sequentially and the ESS required a brief moment to establish the new pointers. Because of this minute processing delay, the data residing on two volumes that were FlashCopied are not exactly time consistent.
FlashCopy consistency groups are used in a single-site scenario in order to create a time-consistent copy of data that can then be backed-up and sent off site, or in a multi-site Global Mirror
for ESS implementation to force time consistency at the remote site.
The implementation of consistency groups is not limited to FlashCopy. Global Mirror
for z/Series (formerly known as XRC or eXtended Remote Copy) also creates consistency groups to asynchronously mirror disk data from one site to another over any distance.
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
feature supported on various IBM storage devices that makes it possible to create, nearly instantaneously, Point in Time copies of entire logical volumes or data sets. The Hitachi Data Systems
Hitachi Data Systems
Hitachi Data Systems is a company providing mid-range and high-end storage systems, software and services. It is a wholly owned subsidiary of Hitachi Ltd. and part of the Hitachi Information Systems & Telecommunications Division....
implementation providing similar function is branded as ShadowImage. Using either implementation, the copies are immediately available for both read and write access.
FlashCopy Version 1
The first implementation of FlashCopy, Version 1 allowed entire volumes to be instantaneously “copied” to another volume by using the facilities of the newer Enterprise Storage Subsystems (ESS).Version 1 of FlashCopy had limitations however. Although the copy or “flash” of a volume occurred instantaneously, the FlashCopy commands were issued sequentially and the ESS required a brief moment to establish the new pointers. Because of this minute processing delay, the data residing on two volumes that were FlashCopied are not exactly time consistent.
FlashCopy Version 2
FlashCopy Version 2 introduced the ability to flash individual data sets and more recently added support for “consistency groups”. FlashCopy consistency groups can be used to help create a consistent point-in-time copy across multiple volumes, and even across multiple ESSs, thus managing the consistency of dependent writes.FlashCopy consistency groups are used in a single-site scenario in order to create a time-consistent copy of data that can then be backed-up and sent off site, or in a multi-site Global Mirror
Global Mirror
Global Mirror is an IBM technology that provides data replication over extended distances between two sites for business continuity and disaster recovery. If adequate bandwidth exists, Global Mirror provides an recovery point objective of as low as 3-5 seconds between the two sites at extended...
for ESS implementation to force time consistency at the remote site.
The implementation of consistency groups is not limited to FlashCopy. Global Mirror
Global Mirror
Global Mirror is an IBM technology that provides data replication over extended distances between two sites for business continuity and disaster recovery. If adequate bandwidth exists, Global Mirror provides an recovery point objective of as low as 3-5 seconds between the two sites at extended...
for z/Series (formerly known as XRC or eXtended Remote Copy) also creates consistency groups to asynchronously mirror disk data from one site to another over any distance.