Evolutionary Improvements with disaggregated Storage in vSAN 8 U1

Disaggregated storage has been beneficial to customers since its introduction with vSAN 7 U1. With vSAN 8 U1, we have continued that innovation trend and added three new critical capabilities to vSAN disaggregated storage. 

Storage disaggregation with vSAN Express Storage Architecture 

Figure 1. vSAN ESA Clusters acting as server and client for disaggregated storage

Disaggregation in vSAN has proven a very robust and successful method for vSAN customers to share vSAN storage resources with other vSAN clusters or compute-only clusters.  In vSAN 8 U1, vSAN disaggregation in vSAN is now compatible with the Express Storage Architecture.  Users can mount remote vSAN datastores living in other vSAN clusters and use an ESA cluster as the external storage resource for a vSphere cluster.  Support of disaggregation in vSAN when using the ESA maintains the interoperability and ease of use our customers have grown to appreciate with disaggregation in vSAN in vSAN’s Original Storage Architecture.

For this release, the use of this feature supports the following cluster connection types

Disaggregation in vSAN limits remain the same for the ESA and the OSA.  They are as follows:

• Client cluster: Up to 5 vSAN datastores connected
• Server cluster: Up to 10 client clusters connected
• Datastore connection host count: Maximum of 128 – consisting of:
  • Hosts in the vSAN server cluster
  • Hosts in client cluster(s)

The features that ESA currently supports will be supported with disaggregation in vSAN. Support of disaggregation in vSAN when using the ESA has similar capabilities and limits but does not support the following:

• Cross-vCenter Server capabilities
• Disaggregation in vSAN over stretched clusters
• Deduplication (as this is not a part of ESA currently)
• Deep rekey encryption capabilities (as this is not a part of ESA currently)

Much like disaggregation in vSAN when using the OSA, Compute-only clusters can connect to and use storage resources in an ESA server cluster without needing vSAN licenses on the client cluster.

As with explicit fault domains that often traverse across ToR switches, ensuring adequate performance is essential, VMware recommends less than 1 ms latency for clusters participating in disaggregation in vSAN.

Support of vSAN stretched clusters with disaggregation in vSAN (OSA)

Figure 2. vSAN Stretched Clusters acting as client and server for disaggregated storage

Many of our customers interested in using the capabilities of disaggregation in vSAN also have grown to rely on the site resilience capabilities of vSAN stretched clusters.  In vSAN 8 U1, we’ve taken this feedback and introduced support for disaggregation in vSAN when using vSAN stretched clusters powered by the vSAN Original Storage Architecture (OSA).  Not only will this support several stretched cluster configurations, but it will also be able to optimize the network paths for specific topologies to improve the performance capabilities of stretched cluster configurations.  

For this release, this feature supports the following cluster connection types

Note: the vSAN stretched cluster must use the OSA.  Support of Stretched clusters with disaggregation in vSAN when using the ESA is not currently supported.

The following connection types are not supported in this release.

• A client cluster that is a compute-only cluster stretched over two sites.
• A client cluster that is a vSAN stretched cluster connecting to a server cluster that is a vSAN standard cluster (not stretched).

As with disaggregation in vSAN on standard vSAN clusters, remote storage access across multiple clusters is fully supported. Disaggregation in vSAN limits remain the same with the introduction of compatibility with stretched cluster environments (for OSA).  They are as follows:

• Client cluster: Up to 5 vSAN datastores connected
• Server cluster: Up to 10 client clusters connected
• Datastore connection host count: Maximum of 128 – consisting of:
  • Hosts in vSAN server cluster
  • Hosts in client cluster(s)

For this configuration using the OSA, the maximum component count for a stretched vSAN server cluster is 288,000.  The same component limit is found on standard OSA clusters (9,000 per host x 32 hosts – where the host count can increase to 64 but the component count does not).

Disaggregation in vSAN connectivity across clusters using multiple vCenter server instances (OSA)

Figure 3. Disaggregated storage being shared across different clusters in different vCenters

Storage disaggregation in vSAN introduces tremendous flexibility for data centers with ever-changing needs.  Customers with environments managed by multiple vCenter Servers want to take advantage of storage disaggregation in vSAN, and with vSAN 8 U1, they can.  vSAN 8 U1 supports storage disaggregation in vSAN across multiple vCenter Servers when using the Original Storage Architecture (OSA).  This will allow vSphere or vSAN clusters managed by one vCenter Server to use the storage resources of a vSAN cluster managed by a completely different vCenter Server. 

Scaling limitations generally remain the same as disaggregation in vSAN using clusters managed by the same vCenter Server.  However, the maximum number of associated hosts per datastore is still set to 128. Still, since the total host count was an aggregation of client and server hosts within a “data center” entity within the vCenter Server, disaggregation in vSAN does not count the hosts living in the cluster managed by the other vCenter Server.  This results in an effective increase in the maximum datastore connection count.

There are scaling limitation additions when using disaggregation in vSAN across vCenter Servers.

• A single client vCenter can consume up to 5 server vCenter Servers to serve datastore sources.
• A single server vCenter can be consumed as datastore sources by up to 10 client vCenter Servers.

To support disaggregated storage connections across vCenters, participating clusters must run vSAN 8 U1 or higher, with all participating vCenter Servers running the latest version. The vCenter Server versions must be identical to maintain API syntax compatibility.  The order of updates (client vCenter server vs. server vCenter server) does not matter. As with disaggregation in vSAN on OSA, client and server connections (datastore mounting) can be bi-directional.  This is omitted from the illustration above for clarity.

As you can see, this dramatically enhances vSAN disaggregated storage capabilities and opens up new avenues of possibilities for our customers. We look forward to seeing all the creative ways you can put these features to use.