HP XP7 Storage - Manual (Page 14)

Related topics
•
For more information about the maximum number of consistency groups that you can create,
see the table in
“Consistency and snapshot groups” (page 9) .
•
For more information about the differences between snapshot groups and consistency groups,
see the table in
“Consistency groups and splitting pairs” (page 10) .
•
For more information about creating consistency groups, see “Creating Fast Snap pairs”
(page 64) .
•
“Pair tasks using the RAID Manager or Remote Web Console” (page 148) .
•
For more information about the RAID Manager commands you can use to store snapshot data,
see
“Pair tasks using the RAID Manager or Remote Web Console” (page 148) .
•
For more information about removing snapshot groups, see “Workflow for removing snapshot
groups” (page 87) .
How snapshot data is stored
The Copy-After-Write (CAW) method is the default method of storing snapshot data. When the
write pending rate in cache memory is 60% or higher, the Copy-On-Write (COW) method is used.
In the CAW method, writing the P-VOL snapshot data changes the status to “write completion”. In
the COW method, storing the P-VOL snapshot data changes the status to “write completion”.
The CAW method wait time is shorter than that of the COW method.
The following figure illustrates the CAW method.
The following figure illustrates the COW method.
14 Overview of Fast Snap