Hi,
I'm not sure why you are getting that exact error message as i'd need more information and would likely have to import the workflow to troubleshoot the issue however it might be help to have a "how to" reference with some screen shots so you can follow along...
In the "create volume" command in your workflow, click on the button on the right side of the "vserver" field so you can set input variables values for the cluster and vserver. EG

Click the "Filter Storage Virtual Machine by Key" filter and set input variable values and click OK (twice to return the the workflow designer). EG

In the workflow designer, click on the "user inputs" tab. Set the input type to "Query" and add a SQL query (this ensures the user can select from a list of clusters\vservers) EG

Cluster:

SELECT
cluster.primary_address,
cluster.name,
cluster.version
FROM
cm_storage.cluster
Vserver:
SELECT
vserver.name
FROM
cm_storage.cluster,
cm_storage.vserver
WHERE
vserver.cluster_id = cluster.id
AND vserver.admin_state = 'running'
AND vserver.cifs_allowed = 1
AND vserver.cifs_is_up = 1
AND (
cluster.primary_address = '${Cluster}'
OR cluster.name = '${Cluster}'
)
As for the volume name, you can increment it using an MVEL function and set a constant for the starting volume name to create if it's the first data volume to be created on the vserver. EG:

Note: set the constant value to match your naming.
Set incremental naming for you volume by clicking on the "incremental naming" button (on the right side of the "name" field" in the "Create Volume" command. EG

In the "incremental naming" wizard click the "enter search criteria" link

Select the approprate filter (EG search for data volumes on the vserver) and click OK

In the incremental naming wizard enter the constant name for the volume (if the filters returned no results) IE set the volume name if no data volumes exist on the vserver. Then select "providing a custom expression" and use the "nextPaddedName" MVEL function to increment the volume name. EG

nextNamePadded(last_volume.name)
The result will be:
- If no volumes exist on the vserver it will create the first volume using the constant value (EG 'volume_001')
- If a volume already exists using the naming standard defined in the constant it will increment the volume name and create the next volume (EG 'volume_002' )
For example:

Hope that helps? Please let me know if you have any questions?
/Matt
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