In a system employing GDS Snapshot, backups can be created using snapshots from proxy volumes during the services operation.
However, to secure consistency of snapshot data, the service must be stopped temporarily when creating a snapshot (when parting a proxy volume from a master volume).
See
For securing consistency of snapshot data, see "A.2.29 Ensuring Consistency of Snapshot Data."
Figure 6.11 Backup Schedule
Note
Instant Restore
If an error occurs in master volume data while the master volume and a proxy volume are joined, the same error occurs in data of the proxy volume and instant restore becomes unavailable. If this happens, you must restore data from tape. After you execute online backup by parting a proxy volume, you are recommended to leave the proxy volume parted until just before re-executing online backup.
Note
Snapshot through Disk Unit's Copy Functions
If groups are hierarchized, or if proxies are in mirroring configuration with the multiplicity of two and higher, copy functions of disk units are unavailable for copying data from masters to proxies. For details, see "A.2.23 Using the Advanced Copy Function in a Proxy Configuration" and "A.2.27 Using Dell EMC TimeFinder or Dell EMC SRDF in a Proxy Configuration."
Note
When Using Dell EMC TimeFinder or Dell EMC SRDF
In the procedures described below, volumes are used for snapshot operations. However, when using TimeFinder or SRDF, use groups for similar operations.
When using TimeFinder, if standard devices that compose the master group and BCV devices that compose the proxy group are established, cancel the BCV pairs prior to joining the master and the proxy.
When using SRDF, have source (R1) devices that compose the master group and target (R2) devices that compose the proxy group split prior to joining the master and the proxy.
After relating the master and the proxy, do not perform TimeFinder or SRDF operations for BCV pairs or SRDF pairs that compose the master and proxy using the SYMCLI command and so on before canceling the relation.
Procedure
1) Joining a proxy volume
To prepare for creating a snapshot, relate and join proxy volume Volume2 as the copy destination of master volume Volume1 to the master volume. This example shows the procedure when Volume1 and Volume2 belong to Class1. Execute the following commands on a node that belongs to the scope of class Class1.
1-1) Stop proxy volume Volume2. If Class1 is a shared class, specify the "-e allnodes" option to stop Volume2 on all nodes.
# sdxvolume -F -c Class1 -v Volume2 |
Information
When using GDS Management View, select a proxy volume and execute [Operation]:[Stop Volume] in the Main Screen.
1-2) Relate and join proxy volume Volume2 to master volume Volume1.
# sdxproxy Join -c Class1 -m Volume1 -p Volume2 |
After returning from the command, synchronization copying from Volume1 to Volume2 is executed.
Information
Relating and Joining a Pair of Groups
If the proxy group includes volumes, remove the volumes before executing the sdxproxy Join command, and also specify the -a option for this command.
Example)
Relate and join proxy group Group2 to master group Group1.
Assign volume names Proxy1 and Proxy2 to the proxy volumes automatically created in Group2 corresponding to volumes Volume1 and Volume2 in Group1.
# sdxproxy Join -c Class1 -m Group1 -p Group2 \ |
See
When using GDS Management View, see "5.2.4.1 Join."
2) Confirming the completion of copying
Confirm that the synchronization copying is complete.
# sdxinfo -S -c Class1 -o Volume2
OBJ CLASS GROUP DISK VOLUME STATUS
----- ------ ------ ------ ------- -------
slice Class1 Group2 Disk3 Volume2 STOP
slice Class1 Group2 Disk4 Volume2 STOP |
If all the displayed slices' STATUS fields are "STOP", synchronization copying is complete.
If the synchronization copying is still in progress, "COPY" will be displayed in the STATUS field.
3) Stopping the services
To secure consistency of snapshot data, stop the services before creating a snapshot and restrain the master volume from being written in.
3a) When the master volume is being used for a cluster application
Inactivate the cluster application.
3b) When the master volume is not being used for a cluster application
3b-1) Stop the services for which the master volume is being used.
3b-2) When the master volume is used as a file system, use either the following methods to prevent write access to the file system. In the following examples, the mount point is /DATA.
To unmount the file system
# cd / # umount /DATA |
To write-lock the file system
# lockfs -w /DATA |
4) Parting the proxy volume
Create a snapshot of master volume Volume1 by parting proxy volume Volume2 from master volume Volume1. Execute the following commands on a node that belongs to the scope of class Class1.
# sdxproxy Part -c Class1 -p Volume2 |
See
When using GDS Management View, see "Part" in "5.3.2.2 Backup (by Synchronization)." For setting of the part environment, select "No" to "Instant Snapshot."
5) Resuming the services
5a) When the master volume is used for a cluster application
Activate the cluster application.
5b) When the master volume is not used for a cluster application
5b-1) When the master volume is used as a file system, use either the following methods to permit write access from applications to the file system on master volume Volume1. In the following examples, the mount point is /DATA.
When the file system was unmounted in step 3b-2), mount the file system.
For the ufs file system
# mount -F ufs /dev/sfdsk/Class1/dsk/Volume1 /DATA |
When write access to the file system was write-locked in step 3b-2), unlock the file system.
# lockfs -u /DATA |
5b-2) Start the services for which the master volume is used.
6) Backing up to tape
Back up the snapshot data on the proxy volume to tape. Execute the following commands on a node that belongs to the scope of class Class1.
See
For details on the backup methods, see the manuals of file systems to be backed up and used commands.
6a) When backing up data held in a raw device with the dd(1M) command
# dd if=/dev/sfdsk/Class1/rdsk/Volume2 of=/dev/rmt/0 bs=32768 |
6b) When backing up the ufs file system with the tar(1) command
6b-1) Before mounting
Check and repair consistency of the ufs file system on the proxy volume with the fsck(1M) command. When the file system on the master volume was unmounted in step 3b-2), skip this step.
# fsck -F ufs /dev/sfdsk/Class1/rdsk/Volume2 |
6b-2) Mounting the snapshot
Mount the ufs file system on proxy volume Volume2 on temporary mount point /DATA_backup.
# mkdir /DATA_backup # mount -F ufs /dev/sfdsk/Class1/dsk/Volume2 /DATA_backup |
6b-3) Backing up to tape
This example shows the procedure when data is backed up to a tape medium of tape device /dev/rmt/0 with the tar(1) command.
# cd /DATA_backup # tar cvf /dev/rmt/0 . |
6b-4) Unmounting the snapshot
Unmount the file system mounted in step 6b-2).
# cd / # umount /DATA_backup # rmdir /DATA_backup |
6c) When backing up the ufs file system with the ufsdump(1M) command
6c-1) Before mounting
Check and repair consistency of the ufs file system on proxy volume Volume2 with the fsck(1M) command. When the file system on the master volume was unmounted in step 3b-2), skip this step.
# fsck -F ufs /dev/sfdsk/Class1/rdsk/Volume2 |
6c-2) Backing up to tape
This example shows the procedure when data is backed up to a tape medium of tape device /dev/rmt/0 with the ufsdump(1M) command.
# ufsdump 0ucf /dev/rmt/0 /dev/sfdsk/Class1/rdsk/Volume2 |
7) Rejoining the proxy volume
To perform online backup again, follow the procedures below on a node that belongs to the scope of class Class1 and then go back to step 2).
7-1) Stop proxy volume Volume2. If Class1 is a shared class, specify the "-e allnodes" option to stop Volume2 on all nodes.
# sdxvolume -F -c Class1 -v Volume2 |
Information
When using GDS Management View, select a proxy volume and execute [Operation]:[Stop Volume] in the Main Screen.
7-2) Rejoin proxy volume Volume2 to master volume Volume1.
# sdxproxy Rejoin -c Class1 -p Volume2 |
After returning from the command, synchronization copying from Volume1 to Volume2 is performed.
See
When using GDS Management View, see "Rejoin" of "5.3.2.2 Backup (by Synchronization)."
8) Breaking the proxy volume
When no more online backup is to be executed, cancel the relationship between master volume Volume1 and proxy volume Volume2. Execute the following command on a node that belongs to the scope of Class1.
# sdxproxy Break -c Class1 -p Volume2 |
See
When using GDS Management View, see "5.5.5 Breaking a Proxy."
