After a successful takeover operation, the secondary cluster (cluster-newyork) becomes the primary for the protection group and the services are online on the secondary cluster. After the recovery of the original primary cluster. cluster-paris, the services can be brought online again on the original primary by using a process called failback.
Sun Cluster Geographic Edition software supports the following two kinds of failback:
Failback-switchover. During a failback-switchover, applications are brought online again on the original primary cluster, cluster-paris, after the original primary cluster's data was resynchronized with the data on the secondary cluster, cluster-newyork.
For a reminder of which clusters are cluster-paris and cluster-newyork, see Figure 2–1.
Failback-takeover. During a failback-takeover, applications are brought online again on the original primary cluster, cluster-paris, and use the current data on the original primary cluster. Any updates that occurred on the secondary cluster, cluster-newyork, while it was acting are primary, are discarded.
Use this procedure to restart an application on the original primary cluster, cluster-paris, after this cluster's data has been resynchronized with the data on the current primary cluster, cluster-newyork.
Before you perform a failback-switchover, a takeover has occurred on cluster-newyork. The clusters now have the following roles:
If the original primary cluster, cluster-paris, has been down, confirm that the cluster is booted and that the Sun Cluster Geographic Edition infrastructure is enabled on the cluster. For more information about booting a cluster, see Booting a Cluster.
The protection group on cluster-newyork has the primary role.
The protection group on cluster-paris has either the primary role or secondary role, depending on whether the protection group could be reached during the takeover.
Resynchronize the original primary cluster, cluster-paris, with the current primary cluster, cluster-newyork.
cluster-paris forfeits its own configuration and replicates the cluster-newyork configuration locally. Resynchronize both the partnership and protection group configurations.
On cluster-paris, resynchronize the partnership.
# geops update partnership-name |
Specifies the name of the partnership
You need to perform this step only once, even if you are performing a failback-switchover for multiple protection groups.
For more information about synchronizing partnerships, see Resynchronizing a Partnership.
On cluster-paris, resynchronize each protection group.
Because the role of the protection group on cluster-newyork is primary, this steps ensures that the role of the protection group on cluster-paris is secondary.
# geopg update protection-group-name |
Specifies the name of the protection group
For more information about synchronizing protection groups, see Resynchronizing a Hitachi TrueCopy Protection Group.
On cluster-paris, validate the cluster's configuration for each protection group.
# geopg validate protection-group-name |
Specifies a unique name that identifies a single protection group
For more information, see How to Validate a Hitachi TrueCopy Protection Group.
On cluster-paris, activate each protection group.
Because the protection group on cluster-paris has a role of secondary, the geopg start command does not restart the application on cluster-paris.
# geopg start -e local protection-group-name |
Specifies the scope of the command
By specifying a local scope, the command operates on the local cluster only.
Specifies the name of the protection group
The -n option must not be given when doing a failback-switchover because the data needs to be synchronized from the current primary, cluster-newyork, to the current secondary, cluster-paris.
Because the protection group has a role of secondary, the data is synchronized from the current primary, cluster-newyork, to the current secondary, cluster-paris.
For more information about the geopg start command, see How to Activate a Hitachi TrueCopy Protection Group.
Before performing the switchover, wait for the data to be completely synchronized.
The data is completely synchronized when the state of the protection group on cluster-newyork is OK. The protection group has a local state of OK when the Hitachi TrueCopy device groups on cluster-newyork have a state of PVOL_PAIR and the Hitachi TrueCopy device groups on cluster-paris have a state of SVOL_PAIR.
To confirm that the state of the protection group on cluster-newyork is OK use the following command:
phys-newyork-1# geoadm status |
Refer to the Protection Group section of the output
On either cluster, perform a switchover from cluster-newyork to cluster-paris for each protection group.
# geopg switchover [-f] -m cluster-paris protection-group-name |
For more information, see How to Switch Over a Hitachi TrueCopy Protection Group From Primary to Secondary.
cluster-paris resumes its original role as primary cluster for the protection group.
Use this procedure to restart an application on the original primary cluster, cluster-paris and use the current data on the original primary cluster. Any updates that occurred on the secondary cluster, cluster-newyork, while it was acting as primary are discarded.
Conditionally, you can resume using the data on the original primary, cluster-paris. You must not have replicated data from the new primary, cluster-newyork, to the original primary cluster, cluster-paris, at any point after the takeover operation on cluster-newyork. To prevent data replication between the new primary and the original primary, you must have used the -n option any time you used the geopg start command.
Before you begin the failover-takeover operation, the clusters have the following roles:
The protection group on cluster-newyork has the primary role.
The protection group on cluster-paris has either the primary role or secondary role, depending on whether the protection group could be reached during the takeover.
Resynchronize the original primary cluster, cluster-paris, with the original secondary cluster, cluster-newyork.
cluster-paris forfeits its own configuration and replicates the cluster-newyork configuration locally.
On cluster-paris, resynchronize the partnership.
# geops update partnership-name |
Specifies the name of the partnership
You need to perform this step only once, even if you are performing a failback-takeover for multiple protection groups.
For more information about synchronizing partnerships, see Resynchronizing a Partnership.
Put the Hitachi TrueCopy device group, devgroup1, in the SMPL state.
Use the pairsplit commands to put the Hitachi TrueCopy device groups that are in the protection group on both cluster-paris and cluster-newyork in the SMPL state. The pairsplit command you use depends on the pair state of the Hitachi TrueCopy device group. The following table gives some examples of the command you need to use on cluster-paris for some typical pair states.
Pair State on cluster-paris |
Pair State on cluster-newyork |
pairsplit Command Used on cluster-paris |
---|---|---|
PSUS or PSUE |
SSWS |
pairsplit -R -g dgname pairsplit -S -g dgname |
SSUS |
PSUS |
pairsplit -S -g dgname |
For more information about the pairsplit commands, see the Sun StorEdge SE 9900 V Series Command and Control Interface User and Reference Guide.
If the command is successful, the state of devgroup1 is given in the output of the pairdisplay command as follows:
phys-paris-1# pairdisplay -g devgroup1 Group PairVol(L/R) (Port#,TID,LU),Seq#,LDEV#,P/S,Status,Fence,Seq#,P-LDEV# M devgroup1 pair1(L) (CL1-A , 0, 1) 12345 1..SMPL ---- ----,----- ---- - devgroup1 pair1(R) (CL1-C , 0, 20)54321 609..SMPL ---- ----,----- ---- - devgroup1 pair2(L) (CL1-A , 0, 2) 12345 2..SMPL ---- ----,----- ---- - devgroup1 pair2(R) (CL1-C , 0,21) 54321 610..SMPL ---- ----,----- ---- - |
.
On cluster-paris, resynchronize each protection group.
Because the local role of the protection group on cluster-newyork is now primary, this step ensures that the local role of the protection group on cluster-paris is secondary.
# geopg update protection-group-name |
Specifies the name of the protection group
For more information about resynchronizing protection groups, see How to Resynchronize a Protection Group.
On cluster-paris, validate the cluster's configuration for each protection group.
# geopg validate protection-group-name |
Specifies a unique name that identifies a single protection group
For more information, see How to Validate a Hitachi TrueCopy Protection Group.
On cluster-paris, activate each protection group in the secondary role without data replication.
Because the protection group on cluster-paris has a role of secondary, the geopg start command does not restart the application on cluster-paris.
# geopg start -e local -n protection-group-name |
Specifies the scope of the command
By specifying a local scope, the command operates on the local cluster only.
Prevents the start of data replication at protection group startup
You must use the -n option.
Specifies the name of the protection group
For more information, see How to Activate a Hitachi TrueCopy Protection Group.
Replication from cluster-newyork to cluster-paris is not started, because the -n option is given on cluster-paris.
On cluster-paris, initiate a takeover for each protection group.
# geopg takeover [-f] protection-group-name |
Forces the command to perform the operation without your confirmation
Specifies the name of the protection group
For more information about the geopg takeover command, see How to Force Immediate Takeover of Hitachi TrueCopy Services by a Secondary Cluster.
The protection group on cluster-paris now has the primary role, and the protection group on cluster-newyork has the role of secondary. The application services are now online on cluster-paris.
On cluster-newyork, activate each protection group.
At the end of step 4, the local state of the protection group on cluster-newyork is Offline. To start monitoring the local state of the protection group, you must activate the protection group on cluster-newyork.
Because the protection group on cluster-newyork has a role of secondary, the geopg start command does not restart the application on cluster-newyork.
# geopg start -e local [-n] protection-group-name |
Specifies the scope of the command
By specifying a local scope, the command operates on the local cluster only.
Prevents the start of data replication at protection group startup
If you omit this option, the data replication subsystem starts at the same time as the protection group.
Specifies the name of the protection group
For more information about the geopg start command, see How to Activate a Hitachi TrueCopy Protection Group.