
Consistency Group FlashCopy
Consistency Group FlashCopy allows you to freeze (temporarily queue) I/O activity to a LUN or volume. Consistency Group FlashCopy helps you to create a consistent
What is Consistency Group FlashCopy?
If a consistent
In order to create this consistent copy, the user issues a set of Establish FlashCopy commands with a freeze option, which will hold off host I/O to the source volumes. In other
words, Consistency Group FlashCopy provides the capability to temporarily queue (at the host I/O level, not the application level) subsequent write operations to the source volumes that are part of the Consistency Group. During the temporary queueing, Establish FlashCopy
is completed. The temporary queueing continues until this condition is reset by the Consistency Group Created command or the
minutes).
Once all of the Establish FlashCopy requests have completed, a set of Consistency Group Created commands must be issued via the same set of DS network interface servers. The
Consistency Group Created commands are directed to each logical subsystem (LSS) involved in the consistency group. The Consistency Group Created command allows the write operations to resume to the source volumes.
This operation is illustrated in Figure
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| DS6000 #1, #2, #3, … | ||
Server1 |
| LSS11 |
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| LSS11 |
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| LSS11 | |
Server2 |
| Wait | FlashCopy | |
write requests | Wait |
| FlashCopy | |
| Wait | |||
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| LSS12 |
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| LSS12 | |
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| LSS12 | |
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| Wait | FlashCopy | |
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| Wait | ||
Waiting write operation | Wait | FlashCopy | ||
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until Consistency Group Created | Consistency Group | |||
command is invoked. |
Figure 6-5 Consistency Group FlashCopy
Chapter 6. Copy Services 95