HP XP7 Storage - Manual (Page 168)

Creating a Snapshot pair
The RAID Manager command for creating a Fast Snap or Snapshot pair is the same as for Business
Copy. However, Fast Snap pair can only operate up to 64 S-VOLs. Therefore, use raidcom command
if you want to operate more than 64 S-VOLs.
The RAID storage system determines whether it is a Business Copy pair or a Fast Snap/Snapshot
pair by the attribute of the S-VOL. The RAID storage system also determines whether it is a Fast
Snap pair or a Snapshot pair by the type of the pool to be used.
A Fast Snap pair is generated in the following two cases:
•
When a V-VOL (OPEN-0V) is specified as an S-VOL.
•
When a pool for Fast Snap is specified as the pool type.
A Snapshot pair is generated in the following two cases:
•
When a V-VOL (OPEN-0V) is specified as an S-VOL.
•
When a pool for Snapshot is specified as the pool type.
A V-VOL has the following characteristics:
•
It appears as "OPEN-0V" to identify a V-VOL easily via the SCSI Inquiry or RAID Manager.
•
A V-VOL unmapped to the S-VOL of a Snapshot will reply to a SCSI Inquiry, but Reading
and/or Writing is not allowed. LDEV will reply the capacity setting as an LU to SCSI Read
Capacity.
•
A V-VOL that has become the S-VOL of a Snapshot will reply to a SCSI Inquiry, and Reading
and/or Writing is allowed.
Snapshot pair status
Each paired volume consists of a primary volume (P-VOL) and a secondary volume (S-VOL). Each
volume has the status for controlling the pair state.
The P-VOL controls the pair state that is reflected on the status of the S-VOL. The major pair statuses
are "SMPL", "PAIR", "PSUS", "COPY", and "RCPY". The status is changed when the RAID Manager
command is issued. A read or write request from the host is allowed or rejected according to the
status.
Table 38 Snapshot Pairing Status
Secondary Primary Pairing Status P-VOL
Status
R/W disable
1
R/W enabled Unpaired (Snapshot) volume SMPL
R/W disable R/W enabled The Snapshot available state allocated the resource. PAIR (PFUL)
R/W disable R/W enabled The preparing state allocates the resource for the Snapshot. COPY
R/W disable R/W enabled The copying state from Snapshot to the primary volume by using
restore option. RCPY
168 Data replication operations with RAID Manager