UR pair operations
You perform different tasks on UR pairs in day to day operations as a Storage Administrator.
Pair operations
You must have Storage Administrator (Remote Copy) role to perform Universal Replicator pair operations. The pair operations are:
Behavior when performing pair operations
You should be aware of the following behaviors when performing pair operations:
- When you perform pair operations between the primary and intermediate sites
or between the intermediate and secondary sites in a 3DC cascade configuration in which
three UR sites are combined, make sure that the pair
operations are not performed in other sites.
If the pair operations are duplicated, either one of the pair operations might fail. When performing pair operations between other sites, make sure the pair status transition to the required status is completed before performing pair operations in another site.
- When a host and the storage system are connected
using Fibre Channel or iSCSI, LU paths must be established for the volume that is subject to
pair operations or for which the pair status is to be checked.
You cannot perform pair operations or check the pair status for a volume for which LU path settings have been canceled.
- When a host and the storage system are connected
using NVMe-oF, set as a namespace the volume that is subject to pair operations or for which
the pair status is to be checked, so that the host can recognize the volume.
You cannot perform pair operations or check the pair status for a volume if the volume is not set as a namespace on the NVM subsystem to which NVM subsystem ports have been added.
- The pair operation cannot be performed during the firmware replacement.
Verify that the firmware replacement is complete, and then perform the pair operation. You can perform the pair operation from CCI even during the firmware replacement.
- The pair operation cannot be performed if the firmware replacement is stopped
when an error occurs or when Cancel is clicked.
Verify that the firmware replacement is complete correctly, and then perform the pair operation. You can perform the pair operation from CCI even when the firmware replacement is not complete.
- If the maintenance operations are performed for the controller boards, or the shared memory is installed or removed on the primary storage system during the initial copy operation after a pair is created or resynchronized, the primary storage system suspends this pair.
- When you use a volume connected to a host using
NVMe-oF, you can use only CCI to create a UR pair.
Also, use CCI to perform the subsequent operations (for example, splitting, resynchronizing, or deleting a pair) on the UR pair. For details about pair operations using CCI, see the relevant topic in the Command Control Interface User and Reference Guide.
- In a 3DC configuration in which three UR sites are combined, a pair operation request might be rejected depending on the status of the UR pair that is linked to the UR pair being operated on.
When operations are available on the UR pair
In a 3DC configuration in which three UR sites are combined, the following tables show whether the UR pair can be operated on depending on the status of the other linked UR pair.
The following table is for the UR pair in a 3DC multi-target configuration in which three UR sites are combined.
| Status of the UR pair linked to the UR pair being operated on | Is the operation available on the UR pair? | |||||
| Create | Split P-VOL specified | Suspend S-VOL specified | Resynchronize P-VOL specified | Resynchronize S-VOL specified | Delete | |
| COPY | No | Yes | Yes | No | No | Yes |
| PAIR | Yes | Yes | Yes | Yes | Yes | Yes |
| PSUS/PSUE | Yes1 | Yes | Yes | Yes | Yes | Yes |
| SSUS/PSUE | No | No | No | No | No | Yes |
| SSWS | No | No | No | No | Yes2 | Yes |
| HOLD | No | Yes | Yes | Yes | Yes | Yes |
Notes:
| ||||||
The following table is for the UR pair in the primary and intermediate sites of a 3DC cascade configuration in which three UR sites are combined.
| Status of the UR pair linked to the UR pair in the primary and intermediate sites | Is the operation available on the UR pair in the primary and intermediate sites? | |||||
| Create | Split P-VOL specified | Suspend S-VOL specified | Resynchronize P-VOL specified | Resynchronize S-VOL specified | Delete | |
| COPY | No | Yes | Yes | No | No | Yes |
| PAIR | No | Yes | Yes | Yes* | Yes | Yes |
| PSUS/PSUE | Yes | Yes | Yes | Yes | Yes | Yes |
| HOLD | No | Yes | Yes | Yes | Yes | Yes |
| HLDE | No | Yes | Yes | Yes | Yes | Yes |
| * If you resynchronize the UR pair in the primary and intermediate sites when the UR pair in the intermediate and secondary sites is in PAIR status, the status of the UR pair in the intermediate and secondary sites is changed to PSUS. | ||||||
The following table is for the UR pair in the intermediate and secondary sites of a 3DC cascade configuration in which three UR sites are combined.
| Status of the UR pair linked to the UR pair in the intermediate and secondary sites | Is the operation available on the UR pair in the intermediate and secondary sites? | |||||
| Create | Split P-VOL specified | Suspend S-VOL specified | Resynchronize P-VOL specified | Resynchronize S-VOL specified | Delete | |
| COPY | No | Yes1 | Yes2 | No | No | No3 |
| PAIR | Yes | Yes1 | Yes2 | Yes | No | No3 |
| SSUS/PSUE | Yes | Yes | Yes | Yes | No | Yes |
| SSWS | No | Yes | Yes | Yes | Yes | Yes |
| HOLD | No | Yes | Yes | Yes | Yes | Yes |
Notes:
| ||||||
In a 3DC cascade configuration in which three UR sites are combined, whether the delta resync processing can be performed on the UR delta resync pair depends on the conditions. For details about the requirements, see Requirements for performing delta resync in 3DC cascade configuration with three UR sites.
Creating a UR pair
When you create a pair, the pair relationship between the volumes is established, and the initial copy operation is performed. The P-VOL remains available to the host for I/O operations during the initial copy operation.
To perform this task in CCI, use the paircreate command.
Before you begin
- You can create a pair only from the primary storage system.
- The S-VOL must be offline to all hosts.
- The primary and secondary storage systems must already be configured, and the remote paths must already be defined.
- The P-VOL capacity and S-VOL capacity must be the same (same number of blocks). To view the capacity in blocks, click in the Logical Devices window. If the capacity is displayed in GB or TB, a slight difference in P-VOL and S-VOL capacity might not be displayed.
- Journal volumes must be registered to the journals that are associated with pairs.
- When creating multiple pairs in a batch, you must set the number of volumes that can be copied concurrently during an initial copy operation in the storage system. .
- If you are creating a UR delta resync pair, see Delta resync configuration .
- Make sure that Performance Monitor is stopped.
The following additional information might be useful to you before beginning the procedure:
- You will select the volumes to be paired by port, host group ID or iSCSI target ID, and LUN ID. Make sure to have this information available.
- You will assign master and restore journals to the P-VOL and S-VOL during the operation.
- You will assign a mirror ID to the pair. This identifies the pair within the journal. A mirror refers to the pair within the journal.
- If the mirror ID you will assign to the new pair contains an existing pair or pairs, the new pair’s volumes must belong to the same primary and secondary storage systems defined in the mirror.
- In a 3DC multi-target configuration in which three UR sites are combined, you cannot create a UR pair with the second mirror if the first UR P-VOL is in the COPY status.
- In a 3DC cascade configuration in which three UR sites are combined, you cannot create a UR pair between the intermediate and secondary sites if the UR S-VOL between the primary and intermediate sites is in the COPY status.
Procedure
In the Explorer pane, expand the Storage Systems tree.
Expand the target storage system tree, expand Replication, and click Remote Replication.
In the UR Pairs tab, click Create UR Pairs.
In the Create UR Pairs window, for Copy Type, select Universal Replicator.
For Remote Storage System, select the secondary storage system’s Model/Serial Number and Path Group ID.
If the mirror contains an existing pair, the same Model/Serial Number as the existing pair’s must be selected.In the Primary Volume Selection box, for Use Existing Volumes of UR Pairs, select whether to use the volume used by the UR pair.
- Select Yes if you are creating a pair in a 3DC multi-target configuration or a pair in a 3DC cascade configuration with three UR sites.
- Select No if you are not creating a pair in a 3DC multi-target configuration or a pair in a 3DC cascade configuration with three UR sites.
In the Primary Volume Selection box, in LU Selection, select the Port ID and Host Group Name or iSCSI Target Alias to display the volumes from which you want to select the P-VOL.
In the Available Primary Volumes table, select the volume that will be the P-VOL.
NoteLimitations for Available Primary Volumes:- When you are using a virtual storage machine with, Available Primary Volumes displays physical LDEV information, not virtual.
- Nondisruptive migration volumes are not displayed in Available Primary Volumes.
- Data volumes in different virtual storage machines cannot be registered in the same journal.
In the Secondary Volume Selection box, for Base Secondary Volume, select the S-VOL’s Port ID, Host Group ID/iSCSI Target ID, and LUN ID.
CautionFor VSP, LUN IDs are displayed in hexadecimal numbers. For VSP 5000 series, VSP G1000, VSP G1500, and VSP F1500, LUN IDs display in decimal or hexadecimal numbers. If you have selected the decimal notation, when assigning an S-VOL in a VSP storage system, make sure to convert the hexadecimal LUN ID number to decimal.For Selection Type, select the method for assigning S-VOLs when multiple primary volumes are selected, Interval or Relative Primary Volume. See "Before you begin" for more information.
For Mirror Selection, specify the following:
For Master Journal, select a number from the list of registered journal IDs. The list excludes already-assigned master and restore journal IDs.
NoteIf you selected Yes for Use Existing Volumes of UR Pairs in the Primary Volume Selection box, Depends on Selected P-Vols is selected for Master Journal.For Mirror ID, assign an identifier number for the mirror.
For Restore Journal, select a number from the list of registered journal IDs. All journal IDs display (000-0FF).
For CTG ID, select a consistency group from the list of those registered in the storage system. An asterisk indicates the CTG is assigned to a pair in the Select Pairs table.
Click Options to define the following optional settings:
For Initial Copy Type, you can specify whether to copy data from P-VOL to S-VOL during the operation.
- Entire creates the pair and copies data to the S-VOL. (Default)
- None creates the pair but data is not copied to the S-VOL. This requires that data in the P-VOL and S-VOL are already identical.
- Delta creates the delta resync pair but data is not copied to the S-VOL.
For Initial Copy Priority, you can specify the scheduling order for this initial copy operation. Range is 1 to 256 (default = 32).
If a time out error occurs, the copy operation may not be executed in the order that you set with Initial Copy Priority. The time out error may be caused by the CU configuration or a remote copy path error. Review the error, release the pair with the error, and then retry the Paircreate operation.In the Error Level list, you can select one of the following system responses if a failure occurs during this operation:
- Mirror, to split all pairs in the failed pair’s
mirror. Mirror is the default.
However, if a volume failure occurs while the pair status is COPY, only the target pair in the mirror is split, even if Mirror is specified.
- LU, to split only the pair that failed.
- Mirror, to split all pairs in the failed pair’s
mirror. Mirror is the default.
When ready, click Add. This moves the new pair to the Selected Pairs table. (To remove a pair from the table, select the pair and click Remove).
Click Finish.
In the Confirm window, review the settings, enter a task name, and then click Apply.
Results
|
Initial Copy Option |
Pair Status Requirement |
|
Entire or None |
COPY or PAIR |
|
Delta |
HOLD, HOLDING |
You can also monitor the progress of the operation by clicking File > Refresh in the menu bar. This updates the information in the list.
Checking the pair status
Every UR operation requires that the pairs have a specific status. You should always check the pair status before performing any UR operation.
Before you begin
- The pair status requirements are listed in the prerequisite information for each procedure (in "Before you begin").
- To review the definitions of the pair statuses, see Pair status definitions.
Procedure
In the Explorer pane, expand the Storage Systems tree.
Expand the target storage system tree, expand Replication, and click Remote Replication.
Select the UR Pairs tab, and then locate the desired pair in the list. The pair status is displayed in the Status column. Click as needed to display the most current pair status information in the Remote Replication window.
To view detailed pair properties, select the pair, and then click .
Splitting a UR pair
When you split a pair, write-data is no longer sent to the S-VOL and the pair is no longer synchronized. Splitting a pair or mirror gives you a point-in-time copy of the P-VOL.
The following information might be useful before beginning the procedure:
- Performing the pair split when I/O load is low reduces impact on performance. Operations on multiple pairs in the same consistency group with different statuses may result in suspension during periods of heavy write I/O.
- If you split pairs in PAIR status and other than PAIR status in the same mirror, an unexpected suspension could occur during the operation under heavy I/O load conditions. You can estimate whether the I/O load is heavy or not from frequency of host I/Os. This operation should be performed under light I/O load conditions.
- During normal operations, the secondary storage system rejects write operations to an S-VOL. If desired, you can enable write operations to the S-VOL while the pair is split by enabling the S-VOL write option. When this option is enabled, the secondary storage system sends the S-VOL track bitmap to the primary storage system during pair resync to ensure proper resynchronization of the pair. The S-VOL write option (Secondary Volume Write) is described in the pair-split procedure.
To perform this task in CCI, use the pairsplit command.
Before you begin
- This operation can be performed from the primary or secondary storage system.
- Pair status must be COPY or PAIR.
- To split multiple pairs at the same time, the pairs must belong to the same mirror. This ensures sequence consistency among S-VOLs in the mirror.
- Pairs in a CCI consistency group consisting of multiple primary and secondary storage systems can only be split in the mirror.
Procedure
In the Explorer pane, expand the Storage Systems tree.
Expand the target storage system tree, expand Replication, and click Remote Replication.
In the UR Pairs tab, select the pairs to be split and click Split Pairs.
In the Split Pairs window, review the pairs to be split in the Selected Pairs table. To remove a pair from the table, select the pair and click Cancel.
For Secondary Volume Write, specify whether data can be written to the S-VOL while it is split. Available only when performing the split operation from the pair’s primary storage system.
- Enable: The host can write data to the S-VOL.
- Disable: The host cannot write data to the S-VOL.
NoteIn a 3DC configuration in which three UR sites are combined, host I/O write requests to the split pair's S-VOL might be rejected when the delta resync pair shares the split S-VOL, even if you split a pair with the Secondary Volume Write option enabled.Click Finish.
In the Confirm window, review the settings, enter a task name, and then click Apply.
Splitting a mirror
A mirror normally has multiple pairs with the same master and restore journals groups. When you split a mirror, you split all the pairs in the mirror. As with a normal pair split, data copying is suspended between primary and secondary journals.
To perform this task in CCI, use the pairsplit command.
Before you begin
- A mirror can be split from the primary or secondary storage system.
- Pair status must be Active.
Procedure
In the Explorer pane, expand the Storage Systems tree.
Expand the target storage system tree, expand Replication, and click Remote Replication.
On the Mirrors tab, select the mirrors to be split and click Split Mirrors.
In the Split Mirrors window, review the mirrors that you selected in the Selected Mirrors table. To remove a mirror, select it and click Cancel.
For Secondary Volume Write, specify whether data can be written to S-VOLs in the mirror while it is split.
- Enable: The host can write data to S-VOLs in the mirror. Available only when the selected mirror’s Attribute is Master. If Restore, Disable is used automatically.
- Disable: The host cannot write data to S-VOLs in the mirror.
For Split Mode, specify whether data is written to S-VOLs in the mirror before the split operation runs.
- Flush: Copies all update data from to S-VOLs in the mirror before the split.
- Purge: Prevents update data from being copied to S-VOLs in the mirror before the split. Uncopied data is copied to the S-VOL when the pair is resynchronized.
Click Finish.
In the Confirm window, review the settings, enter a task name, and then click Apply.
Creating point-in-time copies
Universal Replicator allows you to make Point-in-Time (PiT) copies of volumes in the same journal. Point-in-Time describes a copy of data made at a specific time.
To perform this task in CCI, use the pairsplit command.
Before you begin
- Review the prerequisite information (in "Before you begin") in Splitting a mirror.
Procedure
Stop all write I/Os from hosts to P-VOLs in the journal.
Split the mirror. Make sure to specify Flush for Split Mode.
When the status of all pairs in the journal changes to PSUS, the operation is completed. Resume write I/O to the P-VOLs.
Resynchronizing a UR pair
Resynchronizing a pair copies the differential data of a pair, for which the data copy processing from the primary to the secondary sites stops, to match the data again.
To perform this task in CCI, use the pairresync command.
Before you begin
- This operation is performed from the primary storage system only.
- The pair status must be
PSUS or PSUE.
If pair status is HOLD, HOLDING, or HLDE, use the resynchronizing mirrors operation (see Resynchronizing a mirror ).
- In a 3DC multi-target configuration with three UR sites, you cannot resynchronize the other mirror's UR pair when one mirror's UR P-VOL is in the COPY status.
- In a 3DC cascade configuration with three UR sites, you cannot
resynchronize the UR pair between the primary
and intermediate sites when the UR pair between the
intermediate and secondary sites is in the COPY status, as
illustrated in the following figure.
- In a 3DC cascade configuration with three UR sites, the pair between the intermediate and secondary sites will be split automatically when you resync the UR pair between the primary and intermediate sites, if the UR pair between the intermediate and secondary sites is in the PAIR status.
- Pairs suspended by the system (PSUE status) can be resynchronized only after the error causing the suspension has been corrected.
The following additional information might be useful before beginning the procedure:
- Performing the operation on a pair in HLDE status changes the status to HOLD.
- The primary storage system does not resynchronize a pair that is suspended due to an error until the cause of error is resolved.
- If P-VOL status is Failure and S-VOL status is unpaired, the pair cannot be recovered by resynchronizing. It must be deleted and created again.
- Resynchronizing pairs when I/O load is low reduces impact on performance. Operations on multiple pairs in the same mirror with different statuses may results in suspension during periods of heavy write I/O.
- If you resynchronize pairs in PAIR status and other than PAIR status in the same mirror, an unexpected suspension could occur during the operation under heavy I/O load conditions. You can estimate whether the I/O load is heavy or not from frequency of host I/Os. This operation should be performed under light I/O load conditions.
Procedure
In the Explorer pane, expand the Storage Systems tree.
Expand the target storage system tree, expand Replication, and click Remote Replication.
In the UR Pairs tab, select the pairs to be resynchronized and click Resync Pairs.
In the Resync Pairs window, review the pairs in the Selected Pairs table. You can remove a pair from the table by selecting it and clicking Cancel.
For Copy Priority list, specify the scheduling order for resynchronizing selected pairs, between 1 and 256.
For Error Level, specify the system response if a failure occurs during this operation.
- Mirror:
Splits all pairs in the failed pair’s mirror.
However, if a volume failure occurs while the pair status is COPY, only the target pair in the mirror is split, even if Mirror is specified.
- LU: Splits only the specified pair or pairs that failed.
- Mirror:
Splits all pairs in the failed pair’s mirror.
Click Finish.
In the Confirm window, review the settings, enter a task name, and then click Apply.
Resynchronizing a mirror
When you resynchronize a mirror, the differential data of all the pairs with the mirror ID is copied to match the data again.
When a mirror to which the delta resync pair belongs is resynchronized, the delta resync operation is performed. In a 3DC multi-target configuration using delta resync, if you resynchronize a mirror to perform delta resync, verify that the requirements for performing delta resync are met by referring to the related topics. When you use UR with GAD, resynchronizing the mirror is not necessary for performing delta resync. For more information, see the Global-Active Device User Guide.
To perform this task in CCI, execute the pairresync command by specifying a group.
Before you begin
- Perform this task only from the primary storage system.
- Mirror status must be Stopped, Hold, Holding, or Hold(Failure).
- Device Manager - Storage Navigator does not support multiple primary and secondary storage systems in a UR system. In this case, use CCI to restore a mirror.
- Use CCI to restore a mirror that is in a CCI consistency group containing multiple journals.
- Resynchronizing a mirror when I/O load is low reduces impact on performance.
- If performing the delta resync operation, make sure to review Performing the delta resync operation.
Procedure
In the Explorer pane, expand the Storage Systems tree.
Expand the target storage system tree, expand Replication, and click Remote Replication.
On the Mirrors tab, select the mirrors to be resynchronized, delta resynchronized, or changed from Hold(Failure) to Hold status, and then click Resync Mirrors.
In the Resync Mirrors window, review the mirrors in the Selected Mirrors table. You can remove a mirror from the table by selecting it and clicking Cancel.
Click Finish.
In the Confirm window, review the settings, enter a task name, and then click Apply.
Deleting a UR pair
When you delete a pair, the UR relationship between the P-VOL and S-VOL is released. Only the relationship is affected, the data volumes and their data remain.
To perform this task in CCI, use the pairsplit -S command.
In a delta resync configuration, if you delete some UR pairs without splitting pairs for each consistency group, split and resynchronize them for each consistency group after the deletion.
Before you begin
- You must have the Storage Administrator (Remote Copy) role.
- This operation can be performed from the primary or secondary storage system.
- When S-VOLs are physically attached to the same host as P-VOLs, take the S-VOLs offline before releasing the pair. Doing this avoids confusion and possible error when the host is restarted.
- Pairs must be in Suspend status when their journal is in a CCI consistency group consisting of multiple primary and secondary storage systems. If all pairs in the journal are not in Suspend status, you can delete the desired pairs individually, or select Mirror in the Range field, which deletes all pairs in the pair’s mirror.
The following additional information might be useful to you before beginning the procedure:
- When a pair deletion is initiated, differential data is transferred from the S-VOL, the pair relationship is ended, and the volumes’ status becomes unpaired.
- Pairs should be in PAIR status to ensure data consistency between volumes. However, a pair can be deleted in any status except Suspending or Deleting.
- If you delete a UR pair between the intermediate and secondary sites in a 3DC cascade configuration in which three UR sites are combined, change the status of the mirror between the primary and the intermediate sites to Stopped, or change the status of the pair you want to delete to Suspending.
- If the operation fails, the P-VOL nevertheless becomes unpaired, but transfer of differential data to the S-VOL is terminated.
- If you plan to delete all pairs in the journal and then create another pair, be sure to wait at least one minute after deleting the pairs before creating the new pair.
- Perform pair deletion when write I/O load is low to reduce impact on performance. Operations on pairs with different status in the same mirror may result in suspension during periods of heavy write I/O.
- If you delete pairs in PAIR status and other than PAIR status in the same mirror, an unexpected suspension could occur during the operation under heavy I/O load conditions. You can estimate whether the I/O load is heavy or not from frequency of host I/Os. This operation should be performed under light I/O load conditions.
- In a delta resync configuration with TC, if you release the TC pair, the UR delta resync pair is released as well. If you release the UR pair, the UR delta resync S-VOL is released.
- In a delta resync configuration with GAD, release the pairs in the order of UR pair first, UR delta resync pair second, and then finally the GAD pair.
Procedure
In the Explorer pane, expand the Storage Systems tree.
Expand the target storage system tree, expand Replication, and click Remote Replication.
In the UR Pairs tab, select the pairs to be deleted and click .
In the Delete Pairs dialog box, review the pairs in the Selected Pairs table. To remove a pair from the table, select the pair and click Cancel.
For Delete Mode, Normal is used for UR.
CautionNote the following:- Forced deletion in the primary storage system results in data that was not yet sent to the secondary storage system being deleted.
- Forced deletion in the secondary storage system results in data that was not yet restored being deleted.
- If pair status has not changed to SMPL five minutes after you forcibly delete the pair, delete it again.
- Make sure not to re-create the pair in the first five minutes after forcibly deleting it using the same journals (mirrors), even if pair status is SMPL and journal status is Initial: in this case pair creation could fail and the pair might suspend.
- A time-out error can occur at the time of a forced deletion if I/O is sent to another pair in the same journal and the pair’s status is PAIR or COPY.
Click Finish.
In the Confirm window, review the settings, enter a task name, and then click Apply.
Deleting a mirror
When you delete a mirror, data copying between master and restore journals ends. After deleting the mirror, pairs in the mirror are also deleted.
To perform this task in CCI, execute the pairsplit command with the -S option by specifying a group.
Before you begin
- This operation can be performed from the primary or secondary storage system.
- When you delete a mirror between the intermediate and secondary sites in a 3DC cascade configuration in which three UR sites are combined, change the status of the mirror between the primary and the intermediate sites to Stopped, or change the status of the mirror between the intermediate and secondary sites to Stopped.
- If a journal includes two mirrors in a configuration which
TrueCopy and
Universal Replicator are shared:
- If you specify a mirror in Hold, Holding, or Hold(Failure) status, only the UR pairs of the specified mirror are deleted.
- If you specify a mirror that is not in Hold, Holding, or Hold(Failure) status, UR pairs of both mirrors (including the mirror that you did not specify) are deleted.
Procedure
In the Explorer pane, expand the Storage Systems tree.
Expand the target storage system tree, expand Replication, and click Remote Replication.
On the Mirrors tab, select the mirrors to be deleted, and then click .
In the Delete Mirrors dialog box, review the mirrors in the Selected Mirrors table.
For Delete Mode, specify one of the following:
- Normal: Mirrors are deleted only if the primary storage system can change the mirror status to Initial.
- Force: Mirrors are forcibly deleted even when the primary storage system cannot communicate with the secondary storage system.
Click Finish.
In the Confirm window, review the settings, enter a task name, and then click Apply.
Next steps
Do not create pairs with the same journal for at least five minutes, even if the journal status was Initial; otherwise pair creation could fail and the pair would be suspended.
Managing pairs in a GAD 3DC delta resync environment (VSP 5000 series)
This topic describes GAD and UR pair operations in a GAD 3DC delta resync (GAD+UR) environment.
Executing delta resync
When you specify an S-VOL and suspend (swap suspend) a GAD pair, the GAD S-VOL pair status changes from PAIR to SSWS. After the pair status changes to SSWS, the UR delta resync pair changes to a UR pair, and the copying from the GAD S-VOL to the UR S-VOL starts. This change in the copy source of the UR pair is the delta resync operation.
For details about storage system support (models, microcode) for GAD+UR operations, see the Global-Active Device User Guide.
- Pair status and mirror status must be as follows:
Pair type
Pair status
Mirror status
P-VOL
S-VOL
Master journal
Restore journal
GAD pair
PAIR
PAIR
Not applicable
Not applicable
UR pair
PAIR
PAIR
PJNN
SJNN
UR delta resync pair
PSUS*
SSUS*
PJNS
SJNS
* If you use Device Manager - Storage Navigator to suspend (swap suspend) the pair, make sure the status of the UR delta resync pair is HOLD.
- All the differential data of the UR pairs is stored in the primary site's journal.
- Data must be able to be transferred between the UR P-VOL and S-VOL.
- The number of S-VOLs in the UR pairs is the same as that in the UR delta resync pairs.
- There is no failure in the remote path between the secondary site of GAD and the secondary site of UR.
- After creating the UR pair, you must keep updating I/O from the server to the GAD pair's P-VOL or S-VOL for about two minutes.
pairsplit -g oraHA -RS -IH1
Notes on delta resync
- When a UR pair has not been suspended and resynchronized for a long time, the data in the restore journal might exceed 70% of capacity. If this happens, old journal data is automatically deleted. In this case, the P-VOL and S-VOL are not synchronized completely by just copying the data, and delta resync will fail. In case of delta resync failure, resynchronize the UR pair.
- Journal data might be deleted in the following cases, even if the data in the restore journal does not exceed 70% of capacity:
- When you update the P-VOL after resynchronizing the GAD pair.
- When you update the P-VOL after resynchronizing the UR pair between the primary site and UR secondary site.
- When retry-processing occurs because of a delay of the P-VOL update.
- When the update of a GAD S-VOL is delayed.
- If the pair status of the UR delta resync pair does not change after the delta resync operation, the prerequisites for delta resync might not be satisfied. Review the prerequisites for the pair status of the GAD pair, UR pair, and UR delta resync pair.
In case of delta resync failure
If delta resync fails, the UR delta resync pair changes to a UR pair. The status of each pair changes as follows:
In case of delta resync failure, confirm the following two conditions:
- The system requirements for the GAD+UR configuration are met.
- The system has no failure causes.
If you resynchronize the UR pair after delta resync failure, the initial copy is performed for the GAD pair's S-VOL data to the UR pair's S-VOL.
Resynchronizing GAD pairs in a GAD 3DC delta resync environment
To resynchronize a GAD pair by specifying the S-VOL (swap resync), the conditions specified below must be met.
For details about storage system support (models, microcode) for GAD operations, see the Global-Active Device User Guide.
- Pair status must be as follows:
Pair type
Pair status
P-VOL
S-VOL
GAD pair
PSUS
SSWS
UR pair
PSUE or PAIR
PSUE or PAIR
UR delta resync pair
No condition
No condition
- The UR pair whose volume shared by GAD S-VOL after swap resync must be a UR delta resync pair.
pairresync -g oraHA -swaps -IH1
Deleting GAD pairs in a GAD 3DC delta resync environment
For details about storage system support (models, microcode) for GAD+UR operations, see the Global-Active Device User Guide.
Before you begin
If you need to delete a GAD pair forcibly, first delete the UR pair and the UR delta resync pair, and then delete the GAD pair forcibly.
Procedure
Delete the UR pair.
NoteIf you accidentally delete the UR delta resync pair in this step before deleting the UR pair, the UR pair might be suspended by failures.Delete the UR delta resync pair.
Suspend the GAD pair.
Delete the GAD pair.