Tape drive multipath connect

[TakahiroShimomukai]

Hi everyone,
I would like to hear your opinion.

4 node cluster and Tape-SAN environment.
Does Storage System in this KB mean Cluster? Or is it node (controller) ?

https://kb.netapp.com/Advice_and_Troubleshooting/Data_Protection_and_Security/ONTAP_Multi-path_support_for_NDMP_tape_backups

The technical case answer was Cluster.
If node1 and node2 connect the tape drive with single path, node3 and node4 cannot connect to the tape drive.
I can't believe.

So what does multipath mean in this KB?

I am confused.

Thanks

[Ontapforrum]

My opinion - "Storage System" is a whole unit (Cluster), so the technical case answer is correct. I think that kb is suggesting - By multipath, it  means that you can have max '2' paths to the single tape-library(drive). If you have multiple tape-library(drive), then you can connect the other Nodes to those. Also, I think multiple paths does not mean multi-streams from one backup-object, it is only available as a secondary path, in case the backup fails on the current path.

This is also indicated in the following doc:
https://docs.netapp.com/us-en/ontap/tape-backup/configure-multipath-access-concept.html

Ex-
NetApp:
Cluster     = STSW-3070-2_cluster
Node         = STSW-3070-2_cluster-01
Initiator   = 0b [1st path]
Initiator   = 0d [2nd path]
Target =      IBM 3573-TL_1

[TakahiroShimomukai]

Thank you for your opinion.

As there is LAN free backup as a system requirement, I want to do local NDMP backup from each node. I want to share the Tape Drives with 4 node.

configuration 1.
node1:0e  --> switch1 --> TapeDrive1,TapeDrive2
node2:0e  --> switch2 --> TapeDrive1,TapeDrive2
node3:0e  --> switch1 --> TapeDrive1,TapeDrive2
node4:0e  --> switch2 --> TapeDrive1,TapeDrive2

The supported configuration is this, but node1 and node2 cannot use the TapeDrive2 when node3 and node4 are not using the TapeDrive2.

configuration 2.
node1:0e  --> switch1 --> TapeDrive1
node2:0e  --> switch2 --> TapeDrive1
node3:0e  --> switch1 --> TapeDrive2
node4:0e  --> switch2 --> TapeDrive2

Why ONTAP doesn't support the configuration 1. Is it because ONTAP manages the Tape Drive paths across the cluster?
But which drive to use is specified by the DMA. Isn't it the node that operates the Tape Drives?


DEBUG: DMA>>S V4 sequence=11 (0xb)
DEBUG:      Time_stamp=0x634dfe2d (Oct 18 10:15:25 2022)
DEBUG:      message type=0 (NDMP4_MESSAGE_REQUEST)
DEBUG:      message_code=0x300 (NDMP4_TAPE_OPEN)
DEBUG:      reply_sequence=0 (0x0)
DEBUG:      error_code=0 (NDMP4_NO_ERR)
DEBUG:      device=/cluster1-02/rst0a    <---- node & tape name, tape name is node local
DEBUG:      mode=1 (NDMP4_TAPE_RDWR_MODE)

Thanks

[Ontapforrum · Accepted solution]

Configuration -2 :Looks fine to me. I don't know which Ontap version your filer is running but SVM-scope NDMP is what is recommended in the newer version.

In SVM-scope - If your backup application supports the CAB extension and a volume and the tape device share the same affinity, then the backup application can perform a local backup or restore operation, instead of a three-way backup or restore operation. According to config-2, all the volumes that are local to the Node where tape-drive is located will be backed up, this is what we want, so that the backup is local to the Node. 

Please note, the path for a given backup job is defined by the (DMA/Backup Software) Data Management Application without user intervention, depending on volume and tape colocation.

With the CAB extension supported by the backup application, the NDMP server provides affinity information about volumes and tape devices. Using this affinity information, the backup application can perform a local backup instead of a three-way backup if a volume and tape device are located on the same node in a cluster.

This is an old TR, but lot of the information in it still holds good.

NDMP in Clustered Data ONTAP for Tape Backup Software Applications | TR-4376 | NetApp