This section explains how creating portals on Qumulo clusters, and establishing relationships between spoke and hub portals, enables Global Namespace functionality in Qumulo Core.

Qumulo clusters can take advantage of the Global Namespace functionality that lets clusters across disparate geographic or infrastructural locations (on-premises and in the cloud) access the same data while maintaining independent namespace structures on each cluster (for example, by setting only a portion of the cluster’s file system as the portal root directory).

To enable Global Namespace functionality, you must define a spoke portal on one cluster, a hub portal on another cluster, and then propose a portal relationship between the two.

Key Terms

The following key terms help define the components of Global Namespace functionality in Qumulo Core.

  • Spoke Portal Root Directory, Hub Portal Root Directory: A directory on a cluster that uses a portion of its file system for the hub portal or spoke portal.

    According to the file system permissions that a hub portal might impose, you can access a portal root directory by using NFSv3, SMB, or the Qumulo REST API.

  • Spoke Portal: An interface point on a Qumulo cluster that accesses a portion of the file system on another cluster (which has a hub portal). A directory on a cluster defines the root directory for spoke portal. The spoke portal initiates the creation of a hub portal.

  • Hub Portal: An interface point on a Qumulo cluster that shares a portion of its file system with another cluster (which has a spoke portal). A directory on a cluster defines the root directory for hub portal. The spoke portal initiates the creation of a hub portal.

  • Portal Relationship: A proposal that a spoke portal on one Qumulo cluster issues to another Qumulo cluster (which will have a hub portal), which the Qumulo cluster with the hub portal authorizes.

  • Cluster: Any Qumulo cluster that shares a portion of its file system for a hub portal or a spoke portal. A directory on a cluster defines the root directory for a spoke portal or a hub portal.

Portal States

Throughout the process of creating a spoke portal and proposing a portal relationship, either portal type can be in one of the following states.

State Description
Unlinked Qumulo Core has created the spoke portal, but hasn't established a relationship for it. Use the qq portal_propose_hub command.
Pending Qumulo Core has established a relationship between the spoke portal and a hub portal, but the hub portal hasn't given its authorization. Use the qq portal_authorize_hub command.
Active The portal relationship is operational for both clusters and the spoke portal root directory is accessible if full connectivity is established.
Ended The spoke portal root directory is inaccessible because the relationship between the hub portal and spoke portal was removed.

Working with the Global Namespace Functionality

When the hub portal authorizes the portal relationship, the contents of the hub portal root directory become available to the spoke portal immediately.

The first time a client accesses a spoke portal root directory, the spoke portal begins to read and cache data from the hub portal. Subsequent access to the same data accesses the cache of the spoke portal host cluster, with performance characteristics equivalent to access to non-portal data on the spoke portal host cluster. Caching takes place on demand, when a client with access to the spoke portal accesses new portions of the namespace that the hub portal provides. For more information, see Configuring Cache Management for Spoke Portals in Qumulo Core.

To ensure strict consistency, the system uses a proprietary locking synchronization mechanism to ensure that any changes made on the hub portal become available immediately to any client reading this data from the spoke portal.

Qumulo Core enforces permissions in the same way for files and directories in the spoke portal root directory and the hub portal root directory.

You can remove the portal relationship from either the spoke or hub portal.

  • If you remove the spoke portal, Qumulo Core also deletes its root directory, reclaims the capacity consumed by cached data, and the hub portal enters the Ended state.

  • If you remove the hub portal, all data transfer to the spoke portal stops immediately and the spoke portal enters the Ended state (however, its cached data is present but inaccessible).

Example Global Namespace Scenarios

The following are examples of some of the most common scenarios for workloads that use Global Namespace functionality.

Edge Clusters

In this scenario, you deploy a single, large central cluster at your organization’s data center and multiple, small edge clusters at your organization’s branch offices or in remote locations.

A diagram for an example scenario that uses the Global Namespace functionality for an edge cluster

The Global Namespace functionality lets you make the data on the central cluster available to the remote clusters without the need to replicate data to each location. The data remains available to the edge clusters even if their capacity is lower than that of the central cluster.

Active Workload with Archive

In this scenario, several clusters serve active workloads but require access to a large data archive after the initial workflow completes.

Active Workload with Archive

The Global Namespace functionality lets you:

  • Move your cold (infrequently accessed) data to a central archive cluster and then provide access to this data by using a portal on the original cluster.

    The active workload clusters can reclaim most of the data set capacity that was tiered to the data archive cluster. In other words, it is possible to access all the data as before, while using only the capacity on the active workload clusters for the data that your system reads through the portal.

  • Serve specific archive capacity and performance needs by scaling the archive cluster independently of any active workflow clusters.

Known Limitations of the Global Namespace Functionality in Qumulo Core

General

  • Currently, it is possible to configure and manage Global Namespace functionality only by using the qq CLI.

File System

  • A Qumulo cluster can be a portal host for any number of hub portals or for a single spoke portal. It isn't possible for a Qumulo cluster to be a host for spoke and hub portals simultaneously.

  • To ensure strict consistency with the hub portal, all file system objects under the spoke portal root directory are read-only.

  • Only system administrators can access the files and directories that cluster-local users own on the hub portal host cluster.

Data Caching

  • Although first-time data access to data in the spoke portal root directory is subject to round-trip latency between the spoke portal host cluster and the hub portal host cluster, subsequent access to the data is faster. Making changes to data under the hub portal root directory is also subject to latency when the system recaches these changes upon access.

  • The cache of a spoke portal is inherently ephemeral. You must not use it in place of data replication or backup.

  • Future Qumulo Core upgrades might remove cached data from the spoke portal, which can result in a temporary increase in data access latency.

Portal Connectivity

  • A spoke portal is inaccessible without full connectivity between the two clusters in a portal relationship.

  • A spoke portal is inaccessible if the hub portal host cluster and the spoke portal host cluster run different versions of Qumulo Core.

Protocols

  • It isn't possible to create a spoke portal on a cluster with the NFSv4.1, FTP, or S3 protocols enabled or to enable these protocols on an existing spoke potal host cluster.

  • Protocol locks don't synchronize between the hub portal host cluster and the spoke portal host cluster. Specifically, NFSv3 or NLM byte-range locks, SMB share-mode locks, SMB byte-range locks, and SMB leases function independently on the two clusters.

  • Qumulo Core doesn't send SMB2 CHANGE_NOTIFY messages for changes within the spoke portal root directory.