Your virtual cluster state would help you determine.  Using webui under “system configuration” -> clustering -> Virtual Clusters tab -> Virtual cluster State

Clustering active-standby mode means:
     - ALL VCIDs are master on the Array 1
     - ALL VCIDs  are backup on the Array 2
    Note: both Array 1 and Array 2 should have the same VCID

Sample output on Array 1:
     Interface name: outside
     Virtual Cluster ID (VCID): 7
     Virtual Cluster enable: on
     Virtual Cluster State: Master

Sample output on Array 2:
     Interface name: outside
    Virtual Cluster ID (VCID): 7
    Virtual Cluster enable: on
     Virtual Cluster State: Backup

 
Clustering active-active mode means:
     - Minimum of two VCIDs peer unit
     - Two VCIDs should corresponding to two different Virtual IPs

Sample output on Array 1:
     Interface name: outside
     Virtual Cluster ID (VCID): 7
     Virtual Cluster enable: on
     Virtual Cluster State: Master
       *Sample Virtual IP: 192.168.2.100

     Interface name: outside
     Virtual Cluster ID (VCID): 8
     Virtual Cluster enable: on
     Virtual Cluster State: Backup
    *Sample Virtual IP: 192.168.2.101

 Sample output on Array 2:
     Interface name: outside
     Virtual Cluster ID (VCID): 7
     Virtual Cluster enable: on
     Virtual Cluster State: Backup
      *Sample Virtual IP: 192.168.2.100

    Interface name: outside
    Virtual Cluster ID (VCID): 8
    Virtual Cluster enable: on
    Virtual Cluster State: Master
      *Sample Virtual IP: 192.168.2.101