HP StorageWorks XP24000 Continuous Access Journal Software User and Reference Guide, v01 (T5278-96001, June 2007)

secondary s ite will be made in the same order that updates to the Continuous Access Synchronous
P-VOL in the primary site are made.
As explained above, when the host in the primary site issues an I/O request to the Continuous Access
Synchronous P -VOL, the data will be restored asynchronously to the Continuous Access Journal secondary
data volume in thesecondarysiteataremote location.
S-VOL/
Primary data
volume
Master
JNLVOL
Restore
JNLVOL
Primary site
Intermediate
site
Secondary
site
P-VOL
Secondary
data volume
I/O
I/O finished
Transfer
asynchronously
Transfer
synchronously
Finished storing
data
Figure 25 B a sic Behavior in a 3DC C asca ding Configuration
If a Continuous Access Synchronous pair is suspended in a 3 DC cascading configuration, you will
be able to resynchronize the pair by using a differential copy. If a Continuous Access Journal pair is
suspended, you will be able to resynchronize the pair by using the differential copy.
Note: To per form disaster recovery from a failure at the primary site in a 3DC cascading configu ration,
you must ensure that the fence level of the Continuous Access Synchronous P-VOL is Data.If this fence
level is specified, you can perform disaster recovery by using the Continuous Access Journal secondary
data volume that contains the data stored in the Continuous Access Synchronous P-VOL.
Hardware Configuration
This section explains the hardware configuration for a 3DC cascading configuration using Continuous
Access Synchronous and Continuous Access Journal. In a 3 D C cascading configuration, three storage
systems are required. HP recommends that RAI D Manager be installed on hosts at the primary site, the
intermediate site, and the secondary site. Remote Web Console computers are required for these sites.
The foll
owing explains the hardware configurations at these sites:
• Primary site
• The storage system must have Continuous Access Synchronous installed.
•The sto
rage system must have a Continuous Access Synchronous P-VOL.
• Intermediate site
• The storage system must have Continuous Access Synchronous installed.
•The sto
rage system must have Continuous Access Journal installed.
• The storage system must have a volume used as both a Continuous Access Synchronous S-VOL
and a Continuous Access Journal primary data volume.
•The st
orage system musthaveaContinuous Access Journalmasterjournal volume.
• Remote site
• The storagesystem musthaveContinuousAccess Journalinstalled.
•The st
orage system must have a Continuous Access Journal secondary data volume.
• The storage system must have a Continuous Access Journal restore journal volume.
Setup Procedure
This section explains the procedure for setting up a 3DC cascading configuration using Continuous
Access Synchronous and Continuous Access Journal.
To set up a 3DC cascading configuration:
60
Preparing for Continuous Access Journal Operations