Tuesday, September 15, 2020

vSAN 7 Update 1 - What's new

vSAN 7 Update 1 has been announced, so let's look at what it brings into the table. 


In the figure below, you will see what new features are available in this release.

New features in vSAN 7 Update 1

VMware HCI Mesh

It is a possibility to mount remote vSAN datastore from external (aka Server) vSAN Cluster to multiple Client vSAN Clusters. An example topology is depicted in the figure below.


HCI Mesh allows multiple client vSAN clusters can mount and share a remote datastore from vSAN Server Cluster. A single datastore can be mounted up to a maximum of 64 hosts, including the server cluster's hosts. With such topology, you can do vMotion (Compute only) across multiple vSphere/vSAN Clusters.

With HCI Mesh you can also do a Full Mesh where vSAN Cluster acts as Client and Server of HCI Mesh. Such topology is depicted below, where all three clusters are both clients and servers.

Full Mesh

Such Full Mesh topology is ideal for homogeneous clusters and equalizes storage consumption across clusters. Scalability of such topology is limited to 5 remote datastores and 5 client datastores. In other words, Client clusters can mount a maximum of 5 remote datastores, and Server clusters can export up to a maximum of 5 client clusters.

Few more notes about HCI Mesh 

  • HCI Mesh Client server is vSAN Cluster. So, the minimum node count is 2-node vSAN Cluster
  • Compute-only vSAN cluster technically works but not recommended and supported at the moment.
  • Meshing Hybrid and All-Flash datastores is supported

vSAN Native File Services

VMware is extending vSAN File Services to SMB protocol. SMB is integrated with Microsoft Active Directory and supports Kerberos authentication. This means that vSAN now supports NFS (version 3 and 4.1) and SMB.


vSAN Data-in-Transit Encryption

vSAN 7 Update 1 increases overall security with native Inter-node encryption of vSAN data traffic over TCP, which ensures data privacy, authentication, and integrity, leveraging existing FIPS-2 validated crypto module. The interesting fact is, that external Key Management Server (KMS) is not required for this feature. However, please be aware that vSAN Mesh and Data-in-Transit Encryption together are not supported in this release.

vSAN Data-in-Transit Encryption

SSD Secure Erase (Secure wipe method)

vSAN 7 Update 1 has the option to securely erase SSDs for Dell and HPE supported devices at this release, so HPE & Dell vSAN Ready Nodes and DellEMC VxRail should be able to use this feature. Other hardware vendors will obviously come in the future.


Overall performance optimization

Based on VMware internal performance tests, vSAN 7 Update 1 should be approximately 30% faster in comparison to vSAN 6.7 U3, which was the fastest vSAN release so far. I know this is a kind of vague statement without further details but I personally believe, the vSAN performance, especially in the All-Flash model, was already good enough for the majority of traditional workloads. Of course, additional performance improvements are always nice to have but I think there are other factors which are more important at least for customers I work with. 


vSAN prior 7 Update 1 supported compression together with deduplication. vSAN 7 Update 1 decouples the compression feature from the deduplication feature to allow space efficiency with a lower performance overhead caused by the deduplication algorithm. 

When both features (Dedup & Compress) are turned on, it works in the following way ... 


  • Per disk group
  • Occurs when destaging to the capacity tier
  • 4KB fixed blocks


  • Occurs after dedup, prior to data being destaged
  • If block is compressed <= 2KB
  • Otherwise full 4KB block is stored

When Deduplication is Turned On, the failure domain is the whole disk group.
In Compression-only mode, the failure domain is reduced to a disk, which is another benefit improving availability, reducing data to resync on failures, therefore improves availability and recoverability SLA.

Compression-only has a significantly higher performance than dedup, that's why OLTP workloads primarily benefit from this feature.


Enhanced Durability During Maintenance Operations

First of all, it is important to understand the difference between Durability and Availability. We are talking here about Durability during vSphere/vSAN Cluster node maintenance mode. The feature is nicely depicted in the figure below.

Enhanced Durability During Maintenance Mode

When ESXi host enters Maintenance Mode you can do 
  • Full data Evacuation <-- time-consuming operation but vSAN objects stay protected per Storage Policy intent
  • Ensure Availability <-- it checks that none vSAN object becomes unavailable, but can become unprotected
  • Nothing <-- this is very dangerous and can cause a data loss
Now with vSAN 7 Update 1, you can Ensure Availability, acknowledge that some vSAN objects can become unavailable in case of some other failure, but doing delta writes to other Host or Failure Domain for the vSAN object placed on a host with the only active replica. This results in additional durability protection (prevents loss of data) because, in the case of Replica 1 failure, the vSAN object becomes unavailable, but you can recover the data very quickly from Replica 2 and Delta Writes after the ESXi host returns back from the planned maintenance mode.

Implementation details:
  • Only available when another Host or Failure Domain is available
  • Can be the same host as the witness component
  • Applies to both RAID Mirroring and Erasure Coding
Faster Host Reboots and Cluster Upgrades
  • Significant improvement in cluster upgrades due to faster host reboots
  • Host metadata is written to disk before a reboot and read back to memory after reboot. This is faster than rebuilding metadata.
  • Average 5x improvement in host reboot times

Shared Witness for 2 Node vSAN Deployments

This feature enables 2-Node vSAN deployments to share a common witness instance. vSAN 7 Update 1 supports up to 64 ROBO 2-Node clusters. With vSAN witness consolidation, customers can reduce deployment cost and operational complexity.

Slack Space optimized, operationalized, and renamed into Reserved Capacity

In the past, VMware recommended keeping 25% - 30% capacity as slack space. Now, the new Reserved Capacity is optimized to requires less space and is dependent on deployment variables and decreases with the number of hosts in vSAN Cluster. Example deployment:
  • 12 node cluster = ~16%
  • 24 node cluster = ~12%
  • 48 node cluster =~ 10%
Reserved capacity is required for:
  • Resync operations such as policy changes, rebalancing, and data movement
  • Rebuild activities due to failures
Slack space is Reserved Capacity

On top of disk space optimization for reserve capacity, vSAN now optionally prevents the consumption of vSAN reserved capacity with optional capacity reserves including
  • Operations reserve
  • Host rebuild reserve
Capacity reserves are soft-thresholds that prevent provisioning activities, thus existing VM I/O is not prevented. And once again, this prevention is completely optional, so it is OPT-IN setting and it is not enabled by default. You can see UI in the figure below.

Please note that the vSAN Reserved Capacity feature is not supported on stretched clusters and 2-node vSAN.

vLCM Enhancements

Dell and HPE are supporting vLCM since vSAN 7 release. Now, in vSAN 7 Update 1, Lenovo ReadyNode models are supported as well.

From the technical features point of view, vLCM has been enhanced in the following areas 
  • vSAN Fault Domains, 2-node, and Stretched Clusters awareness
  • hardware compatibility pre-checks
  • parallel cluster remediation of up to 64 clusters
  • support for environments running NSX-T 3.1
The technical features above are depicted in the following figure.


Simplified Routing for vSAN Network Topologies

Prior to this release, vSAN topologies with external witness had to use static routing in each ESXi host which was a significant management pain. In vSAN 7 Update 1, alternate default gateway can be specified and static routes do not need to be used. This is a very useful feature from an operational point of view if you ask me.

vSAN alternate default gateway

vSAN I/O Insight

This is another very useful feature, to analyze storage workload I/O patterns. It is
  • Quick and easy tool in vSphere Client to capture workload IO characteristics on VSAN
  • Rich IO Pattern metrics and histograms to analyze R/W ratio, Seq/Random ratio, 4K aligned / unaligned ratio, IO size distribution
  • Finer granular IO performance metrics
The tool provides solid data points for the infrastructure team to triage issues with app users without the need for complex external tools. See. the screenshot below.

vSAN IO Insight


vSAN 7.0 U1 release is definitely a significant step forward for VMware software-defined storage, which is an important component of full VMware SDDC stack. And this is a very nice proof of a key SDDC benefit ... Quick response to customers and industry requirements ... This is the reason, why I really like software-defined and hyper-converged infrastructure, leveraging commoditization, integration, and continuous product improvement. vSphere administrator is the king of the house ... at least from the infrastructure point of view :-)

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