Hp XP P9500 Storage User Manual download pdf (Page 142)

The host issues an update to the Cnt Ac-S primary volume (P-VOL), which is copied synchronously

to the S-VOL. The Cnt Ac-J system copies the synchronous S-VOL data to the Cnt Ac-J remote site.

Data in the Cnt Ac-J S-VOL is an asynchronous copy of the Cnt Ac-S P-VOL. Depending on RPO

and bandwidth, Cnt Ac-J S-VOL data can be very close to P-VOL data. As always with Cnt Ac-J,

data consistency is ensured.

Figure 21 3-data-center cascade configuration

Failure recovery occurs as follows:

• If a failure occurs at the Cnt Ac-S P-VOL, business continues because data in the Cnt Ac-J

S-VOL is restored to the production system via the intermediate volume, if needed. Update

sequence integrity is ensured.

• If a failure occurs at both Cnt Ac-S P-VOL and S-VOL, an implemented disaster recovery plan

would re-direct host activities to the Cnt Ac-J S-VOL.

See “Recovery for 3 Cnt Ac-J/Cnt Ac-S DC cascade configuration ” (page 97) for recovery

information and procedures.

Prerequisite information for 3DC cascade

• P9500 must be installed at the local, Cnt Ac-S intermediate, and Cnt Ac-J remote sites.

• RAID Manager is recommended at all sites.

• Remote Web Console is required at all sites.

Host application◦

◦ Cnt Ac-S

◦ Cnt Ac-S primary volume (P-VOL), the primary production volume

◦ Cnt Ac-S fence level must be Data .

• The intermediate site requires the following:

Cnt Ac-S◦

◦ Cnt Ac-J

◦ Cnt Ac-S S-VOL = Cnt Ac-J P-VOL

◦ Cnt Ac-J master journal volume

• The remote site requires the following:

Cnt Ac-J◦

◦ Cnt Ac-J S-VOL

◦ Cnt Ac-J remote journal volume

• Differential data is used to re-synchronize a suspended Cnt Ac-S or Cnt Ac-J pair.

• When the Cnt Ac-S pair is recovered, the Cnt Ac-J pair in PAIR or COPY status is automatically

split by the system.

142 Configurations with Continuous Access Synchronous

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Hp XP P9500 Storage User Manual Page 142