HP 3PAR Remote Copy Software - Manual (Page 54)

2.38 Error Handling
Remote Copy User’s Guide InForm OS Version 2.3.1
When synchronous replication is used, low timeout values are used in an attempt to ensure
that replication is stopped before the host I/O begins to time out in case of a network failure. If
the network used by Remote Copy has transient problems, the lower timeout values can result
in repeated link failure alerts and the stopping of all Remote Copy volume groups. If
asynchronous periodic volume groups are in use, then this increased sensitivity is unnecessary
and the longer timeout values allow Remote Copy to continue in the presence of transient
network problems.
2.13.4 Storage Server Failures
If one of the storage servers in a Remote Copy pair fails, it is detected by the other storage
server as a concurrent failure of both communication links and is treated the same as a Double
Link Failure , as described on page 2.36 . When such a failure is detected, the storage server
generates an alert.
2.13.4.1 Failure of a Target
When a target has failed and the data on the secondary volumes needs to be accessed, the role
of the groups containing those volumes must be reversed.
2.13.4.2 Failure of a Secondary Target
The failure of a secondary target in a Remote Copy pair is indistinguishable from the failure of
all communication links to the remote site. The treatment of this error condition is the same as
the handling of a complete network failure or a double link failure, as described in Double
Link Failure on page 2.36. After the secondary target comes back up, if any updates were made
while the target was down, those updates are synchronized after replication is restarted by
issuing the startrcopygroup command on the storage server.
2.13.5 Write Errors
When a write encounters an error on the primary volume, the error is returned to the host as
an I/O failure. If a write completes successfully on the primary storage server but a write error
occurs on the backup volume, it is handled based on the replication mode and the error
handling policy for the volume group.
NOTE: See Volume Group Modes on page 2.22 for descriptions of synchronous
and asynchronous periodic volume groups.