HP P6000 Continuous Access Implementation Guide (T3680-96431, August 2012)

NOTE: An array running XCS version 09534000 or later with the protocol selection set for
Either may have DR groups created with arrays configured for HP-FC or HP SCSI-FCP. However,
the fabric must be set to SID/DID routing protocol only.
The three available options are shown in “Data replication protocol selection” (page 40). The
window indicates the protocol currently selected.
The following guidelines apply when selecting the replication protocol for each indicated task:
• Installing a new array—When initializing a new array with controller software version
09534000 or later installed, the replication protocol defaults to HP SCSI-FCP. The protocol
can be changed to HP-FC if necessary.
• Upgrading an array—When upgrading an array to 09534000 or later from an earlier version
that does not support HP SCSI-FCP, the replication protocol remains at HP-FC regardless of
whether DR groups are present or not.
• Downgrading an array—When downgrading an array from controller software version
09534000 or later to an earlier version that does not support HP SCSI-FCP, you must configure
the fabric for SID/DID then change the data replication protocol to HP FC before downgrading.
These configuration changes must be completed prior to downgrading the array and bringing
the DR groups back online. When changing the protocol, data replication will stop until both
arrays in the HP P6000 Continuous Access relationship are set to a compatible protocol.
Figure 13 Data replication protocol selection
Data replication protocol performance considerations
The HP-FC modified SCSI protocol replicates data using a single round trip as compared to the
two round trips used by the standard SCSI protocol. HP SCSI-FCP follows the standard SCSI
protocol, requiring two round trips to complete a data transfer. The following considerations can
minimize the additional link overhead introduced by the dual round trip required by HP SCSI-FCP.
NOTE:
• The term IP acceleration is used here to collectively refer to the Brocade FCIP FastWrite feature
and the Cisco FCIP Write Acceleration feature.
• IP acceleration can only be used if the replication network between two arrays is using the
HP SCSI-FCP protocol. IP acceleration MUST NOT be enabled when using the HP-FC protocol.
The following information assumes that in both single-network and dual-network link environments
each individual network link is capable of maintaining the solution’s defined RPO. If this is not the
case, each network link is considered a SPOF because the failure of one network link prevents the
solution from meeting its defined RPO. If each network link cannot maintain the solution’s defined
RPO, you must not enable the IP acceleration feature of the Brocade or Cisco FC-IP routers. It is
40 Planning the array configuration