HP XP7 Storage - Manual (Page 15)

Workflow for the CAW method
The following workflow describes the CAW method and how a XP7 storage system stores snapshot
data:
1. The host writes data to a P-VOL.
2. The XP7 storage system returns the write completion status to the host.
3. The XP7 storage system stores snapshot data for the P-VOL in the background.
Workflow for the COW method
The following workflow describes the COW method and how XP7 stores snapshot data:
1. The host writes data to a P-VOL.
2. The XP7 storage system stores snapshot data for the P-VOL.
3. The XP7 storage system returns the write completion status to the host.
Fast Snap pair restoration
You can use FS to overwrite snapshot data in pools to P-VOLs so that the P-VOL content is returned
to the condition it was when you stored snapshot data. Overwriting snapshot data to P-VOLs is
also referred to as restoring FS pairs.
If a failure occurs while restoring FS pairs, you must delete the unneeded snapshot data (see
“Resynchronizing Fast Snap pairs” (page 83) ).
Related topics
•
“Restoring Fast Snap pairs” (page 79) .
•
“The copy threshold option and host server I/O performance” (page 17) .
•
“Fast Snap pair restoration and host server I/O performance” (page 34) .
•
“Workflow for restoring suspended Fast Snap pairs” (page 81) .
•
“Resynchronizing Fast Snap pairs” (page 83) .
Fast Snap pair status
The FS pair status changes as you create, split, or perform other pair tasks, as illustrated in the
following image.
Fast Snap pair status 15