What do you mean by NDMP CAB extension, how does it work really ?
CAB stands for Cluster Aware Backup, and the extension are nothing but a soft
ware feature that allows mutual communication between a Backup Software [DMA] and the NDMP server to make a rational decisions with respect to the locality of the Hosted Volumes and the Tape Drives.
How does a Backup software such as CommVault implements CAB?
DMA Informs = A DMA implementing CAB extensions - Will notify the NDMP Server about the VOLUMEs to be backed up even before a data connection has been established. This happens during NDMP control connection establishment.
NDMP Server responds = This will enable NDMP to identify the Node on which the VOLUME is hosted, so that when the DMA does establish the data connection, NDMP Server will ensure that is established from the appropriate Node hosting the VOLUME.
CAB term is applicable to NDMP SVM Scope Mode only. NetApp Cluster Ontap has two modes of operations:
1. Node-scope mode
2. SVM-scope mode [CAB]
In Node-scope mode = It is flat and simple, you can only backup VOLUMEs hosted on the particular NODE, you cannot see other VOLUMES that are sitting on other NODEs in the Cluster.
In SVM-scope mode = The entire Cluster is available for the Backup, in other words, all the VOLUMEs are exposed irrespective of where they are Hosted.
How does CAB extensions in SVM-scope mode helps in exposing the VOLUMEs and the TAPE drives to DMA?
As mentioned above, in the case of SVM scope NDMP, b'cos the VOLUMEs and TAPEs discovered can be hosted on different NODEs, the CAB extension exposes a 'UID' for each VOLUMEs and TAPEs and this what is called 'AFFINITY' information. If the 'AFFINITY' value of a VOLUME and TAPE match, it can be inferred that the specific VOLUME and TAPE are hosted on the same NDOE. This allows a DMA to DRIVE a LOCAL backup.
Situation can get little murky here - This is b'cos in the SVM-scope mode, there are multiple LIF types available, and depending upon which LIF type you are connecting to during NDMP control connection, you get different VISIBILITY scope.
The visibility of VOLUMEs and TAPEs are determined by the SVM context in which the NDMP control connection is made, basically and the LIF type on which the NDMP control session is established.
Following rules below apply when DMA supports the CAB extension.
In general, the rules set by default is perfect, but may need a tweaking in some scenarios, as shown below, the default settings for ADMIN SVM & DATA SVM:
CAB stands for Cluster Aware Backup, and the extension are nothing but a soft
ware feature that allows mutual communication between a Backup Software [DMA] and the NDMP server to make a rational decisions with respect to the locality of the Hosted Volumes and the Tape Drives.
How does a Backup software such as CommVault implements CAB?
DMA Informs = A DMA implementing CAB extensions - Will notify the NDMP Server about the VOLUMEs to be backed up even before a data connection has been established. This happens during NDMP control connection establishment.
NDMP Server responds = This will enable NDMP to identify the Node on which the VOLUME is hosted, so that when the DMA does establish the data connection, NDMP Server will ensure that is established from the appropriate Node hosting the VOLUME.
CAB term is applicable to NDMP SVM Scope Mode only. NetApp Cluster Ontap has two modes of operations:
1. Node-scope mode
2. SVM-scope mode [CAB]
In Node-scope mode = It is flat and simple, you can only backup VOLUMEs hosted on the particular NODE, you cannot see other VOLUMES that are sitting on other NODEs in the Cluster.
In SVM-scope mode = The entire Cluster is available for the Backup, in other words, all the VOLUMEs are exposed irrespective of where they are Hosted.
How does CAB extensions in SVM-scope mode helps in exposing the VOLUMEs and the TAPE drives to DMA?
As mentioned above, in the case of SVM scope NDMP, b'cos the VOLUMEs and TAPEs discovered can be hosted on different NODEs, the CAB extension exposes a 'UID' for each VOLUMEs and TAPEs and this what is called 'AFFINITY' information. If the 'AFFINITY' value of a VOLUME and TAPE match, it can be inferred that the specific VOLUME and TAPE are hosted on the same NDOE. This allows a DMA to DRIVE a LOCAL backup.
Situation can get little murky here - This is b'cos in the SVM-scope mode, there are multiple LIF types available, and depending upon which LIF type you are connecting to during NDMP control connection, you get different VISIBILITY scope.
The visibility of VOLUMEs and TAPEs are determined by the SVM context in which the NDMP control connection is made, basically and the LIF type on which the NDMP control session is established.
Following rules below apply when DMA supports the CAB extension.
In general, the rules set by default is perfect, but may need a tweaking in some scenarios, as shown below, the default settings for ADMIN SVM & DATA SVM:
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