VMware vSAN 7.0 Update 3c | 27 JAN 2022 | ISO Build 19193900 Check for additions and updates to these release notes.

What's in the Release Notes

Updated on: January 27, 2022

The release notes cover the following topics:

• What's New
• VMware vSAN Community
• Upgrades for This Release
• Limitations
• Known Issues

IMPORTANT: VMware removed ESXi 7.0 Update 3, 7.0 Update 3a and 7.0 Update 3b from all sites on November 19, 2021 due to an upgrade-impacting issue. Build 19193900 for ESXi 7.0 Update 3c ISO replaces build 18644231, 18825058, and 18905247 for ESXi 7.0 Update 3, 7.0 Update 3a, and 
7.0 Update 3b respectively. To make sure you run a smooth upgrade to vSphere 7.0 Upgrade 3c, see VMware knowledge base articles 86447 and 87327.

What's New

vSAN 7.0 Update 3 introduces the following new features and enhancements: 

Developer Ready Infrastructure

• CNS platform improvements. CNS platform has improved performance, scale, and resiliency, including better concurrency for Async CSI queries, better handling of orphan volumes, and improved troubleshooting tools.
• Vanilla Kubernetes support enhancements. Enhancements include vSAN stretched cluster support and topology support.
• vSphere with Tanzu. vSAN 7.0 Update 3 supports ReadWriteMany PVs for Tanzu Kubernetes Grid.
• vDPp improvements. vSAN Data Persistence Platform now supports asynchronous installation and upgrades of partner services. New versions of MinIO and Cloudian are available in this release. Pre-checks when entering maintenance mode and disk decommissioning support are available. 

Simplify Operations

• vSAN cluster shutdown and restart. You now can easily shutdown and restart a vSAN cluster. The Shutdown Cluster wizard performs prechecks, and enables you to review, confirm and track the steps needed before and during shutdown and restart process.
• vLCM enhancements. vLCM's hardware compatibility checks support validation of disk device firmware against the vSAN HCL before applying the desired cluster image. vLCM supports upgrade of vSAN witness host (dedicated) as part of the coordinated cluster remediation workflow for vSAN two-node clusters and stretched clusters.
• Enhanced network monitoring and anomaly detection. vSAN 7.0 Update 3 provides additional network health checks for diagnostics, and enables you to tune network monitoring thresholds. 
• vSAN health check correlation. The new vSAN health correlation engine helps identify the root cause of issues on the cluster. This information can simplify troubleshooting and help you remediate related warnings on the cluster. 
• VM I/O trip analyzer. Visual representation of the vSAN I/O path and related performance information throughout the I/O path enables you to easily diagnose VM performance issues. 
• Improved performance monitoring of PV/FCDs. Performance displays can provide an end-to-end view of Persistent Volumes and First Class Disk performance. 

Platform Enhancements

• Stretched cluster site/witness failure resiliency. This release enables stretched clusters to tolerate planned or unplanned downtime of a site and the witness. You can perform site-wide maintenance (such as power or networking) without concerns about witness availability. 
• Nested fault domains for two-node deployments. This feature provides the ability to make an additional copy of the data within the host in addition to making copies across the hosts in a two-node cluster. This delivers data-availability even after a planned/unplanned downtime of a host and losing a drive or disk group on the surviving host. The policy can be configured though SPBM.
• Stuck I/O enhancements. vSAN gracefully detects stuck I/O (failure of I/O controller to complete an operation) on a host and redirects it to a replica. The vSphere Client alerts you of the condition, so you can migrate workloads non-disruptively and power-cycle the problematic host.
• Encryption key persistence. Encryption keys generated by the Key Management solution can be stored in the TPM chip.
• Access Based Enumeration. vSAN File Services now supports SMB Access Based Enumeration (ABE). ABE restricts directory enumeration based on access privileges configured on the directory. 

VMware vSAN Community

Use the vSAN Community Web site to provide feedback and request assistance with any problems you find while using vSAN.  

Upgrades for This Release

For instructions about upgrading vSAN, see the VMware vSAN 7.0 documentation. 

Note: Before performing the upgrade, please review the most recent version of the VMware Compatibility Guide to validate that the latest vSAN version is available for your platform.

vSAN 7.0 Update 3 is a new release that requires a full upgrade to vSphere 7.0 Update 3c. Perform the following tasks to complete the upgrade:

1. Upgrade to vCenter Server 7.0 Update 3c. For more information, see the VMware vSphere 7.0 Update 3c Release Notes. 
2. Upgrade hosts to ESXi 7.0 Update 3c. For more information, see the VMware vSphere 7.0 Update 3c Release Notes. 
3. Upgrade the vSAN on-disk format to version 15.0. If upgrading from on-disk format version 3.0 or later, no data evacuation is required (metadata update only). 
4. Upgrade FSVM to enable new File Service features such as access based enumeration for SMB shares.

Note: vSAN retired disk format version 1.0 in vSAN 7.0 Update 1. Disks running disk format version 1.0 are no longer recognized by vSAN. vSAN will block upgrade through vSphere Update Manager, ISO install, or esxcli to vSAN 7.0 Update 1. To avoid these issues, upgrade disks running disk format version 1.0 to a higher version. If you have disks on version 1, a health check alerts you to upgrade the disk format version.

Disk format version 1.0 does not have performance and snapshot enhancements, and it lacks support for advanced features including checksum, deduplication and compression, and encryption. For more information about vSAN disk format version, see KB 2148493.

Upgrading the On-disk Format for Hosts with Limited Capacity

During an upgrade of the vSAN on-disk format from version 1.0 or 2.0, a disk group evacuation is performed. The disk group is removed and upgraded to on-disk format version 15.0, and the disk group is added back to the cluster. For two-node or three-node clusters, or clusters without enough capacity to evacuate each disk group, select Allow Reduced Redundancy from the vSphere Client. You also can use the following RVC command to upgrade the on-disk format: vsan.ondisk_upgrade --allow-reduced-redundancy

When you allow reduced redundancy, your VMs are unprotected for the duration of the upgrade, because this method does not evacuate data to the other hosts in the cluster. It removes each disk group, upgrades the on-disk format, and adds the disk group back to the cluster. All objects remain available, but with reduced redundancy.

If you enable deduplication and compression during the upgrade to vSAN 7.0 Update 3, you can select Allow Reduced Redundancy from the vSphere Client.

Limitations

For information about maximum configuration limits for the vSAN 7.0 Update 3 release, see the Configuration Maximums documentation.

Resolved Issues

• vSAN Health cannot find VUM with proxy configured

  When a proxy is configured for vSAN, the vsan-health service falsely reported that VMware Update Manager (VUM) is disabled or not installed.

  This issue is fixed in this release.

Known Issues

The known issues are grouped as follows.

• vSAN Issues

vSAN Issues

• Kubernetes pods with CNS volumes cannot be created, deleted, or re-scheduled during vSAN stretched cluster partition 

  When a vSAN stretched cluster has a network partition between sites, an intermittent timing issue can cause volume information to be lost from the CNS. When volume metadata is not present in the CNS, you cannot create, delete, or re-schedule pods with CNS volumes. vSphere CSI Driver must access volume information from CNS to perform these operations.

  When the network partition is fixed, CNS volume metadata is restored, and pods with CNS volumes can be created, deleted, or re-scheduled.

  Workaround: None.

• Shutdown Cluster wizard displays an error on HCI Mesh compute-ony cluster

  The vSAN Shutdown Cluster wizard is designed for vSAN clusters that have a vSAN datastore and vSAN services. It does not support HCI Mesh compute-only clusters. If you use the wizard to shutdown a compute-only cluster, it displays the following error message:

  Cannot retrieve the health service data.

  Workaround: None. Do not use the vSAN Shutdown Cluster wizard on an HCI Mesh compute-only cluster.

• Remediation of ESXi hosts in a vSphere Lifecycle Manager cluster with vSAN fails if vCenter services are deployed on custom ports

  If vCenter Server services are deployed on custom ports in a cluster with vSAN, vSphere DRS, and vSphere HA, remediation of vSphere Lifecycle Manager clusters might fail. This problem is caused by a vSAN resource health check error. ESXi hosts cannot enter maintenance mode, which leads to failing remediation tasks.

  Workaround: None. 

• When vSAN file service is enabled, DFC-related operations such as upgrade, enabling encryption or data-efficiency might fail

  When file service is enabled, an agent VM runs on each host. The underlying vSAN object might be placed across multiple diskgroups. When the first diskgroup gets converted, the vSAN object becomes inaccessible and the agent VM is in an invalid state. If you try to delete the VM and redeploy a new VM, the operation fails due to the VM’s invalid state. The VM gets unregistered but the inaccessible object still exists there. When the next diskgroup gets converted, there is a precheck for inaccessible objects in the whole cluster. This check fails the DFC since it finds inaccessible objects of the old agent VM.

  Workaround: Manually remove the inaccessible objects. 

  When such failure happens, you can see the DFC task failure.

  1. Identify the inaccessible objects from the failure task fault information.
  2. To ensure that the objects belong to the agent VM, inspect the hostd log file and confirm that the objects belong to the VM’s object layout.
  3. Log in to the host and use the /usr/lib/vmware/osfs/bin/objtool command to remove the objects manually.

  Note: To prevent this problem, disable file service before performing any DFC-related operation.

• esxcli vsan cluster leave command fails to disable vSAN on an ESXi host 

  In some cases, the following command fails to disable vSAN on a member host: esxcli vsan cluster leave

  You might see an error message similar to the following:

  Failed to unmount default vSAN datastore. Unable to complete Sysinfo operation. Please see the VMKernel log file for more details.

  Workaround: Perform the following steps in the vSphere Client to disable vSAN on a single member host:

  1. Place the host into maintenance mode.
  2. Move the host out of the vSAN cluster, and into its parent data center.
     ​ vSAN service on the host is disabled automatically during the movement.
• Cannot extract host profile on a vSAN HCI mesh compute-only host

  vSAN host profile plugin does not support vSAN HCI mesh compute-only hosts. If you try to extract the host profile on an HCI mesh compute-only host, the attempt fails. 

  Workaround: None

• Deleting files in a file share might not be reflected in vSAN capacity view

  The allocated blocks might not be returned back to the vSAN storage instantly after all the files are deleted and hence it would take some time before the reclaimed storage capacity to be updated in vSAN capacity view. When new data is written to the same file share, these deleted blocks might get reused prior to returning them to vSAN storage.

  If unmap is enabled and vSAN deduplication is disabled, the space may not be freed back to vSAN unless 4MB aligned space are freed in VDFS. If unmap is enabled and vSAN deduplication is enabled, space freed by VDFS will be freed back to vSAN with a delay.

  Workaround: To release the storage back to vSAN immediately, delete the file shares. 

• vSAN over RDMA might experience lower performance due to network congestion 

  RDMA requires lossless network infrastructure that is free of congestion. If your network has congestion, certain large I/O workloads might experience lower performance than TCP. 

  Workaround: Address any network congestion issues following OEM best practices for RDMA.

• vCenter VM crash on stretched cluster with data-in-transit encryption

  vCenter VM might crash on a vSAN stretched cluster if the vCenter VM is on vSAN with data-in-transit encryption enabled. When all hosts in one site are down and then power on again, the vCenter VM might crash after the failed site returns to service.

  Workaround: Use the following script to resolve this problem: thumbPrintRepair.py  

• VM migration from VMFS datastore or vSAN datastore to vSAN datastore fails

  When you have Content Based Read Cache (CBRC) enabled, sVmotion or xVmotion might fail to migrate a VM that has one or more snapshots to the vSAN datastore. You might see the following error message: The operation is not supported on the object.
  
  The following messages appear in /var/log/vmware/vpxd/
  
  2021-01-31T17:12:27.477Z error vpxd[18588] [Originator@6876 sub=vpxLro opID=65ef3b53-01] [VpxLRO] Unexpected Exception: N5Vmomi5Fault12NotSupported9ExceptionE(Message is: The operation is not supported on the object.,
  --> Fault cause: vmodl.fault.NotSupported
  --> Fault Messages are:
  --> (null)
  --> )
  -->

  Workaround: Consolidate snapshots, or delete all snapshots before migration.

• vSAN allows a VM to be provisioned across local and remote datastores

  vSphere does not prevent users from provisioning a VM across local and remote datastores in an HCI Mesh environment. For example, you can provision one VMDK on the local vSAN datastore and one VMDK on remote vSAN datastore. This is not supported because vSphere HA is not supported with this configuration.

  Workaround: Do not provision a VM across local and remote datastores.

• The object reformatting task is not progressing

  If object reformatting is needed after an upgrade, a health alert is triggered, and vSAN begins reformatting. vSAN performs this task in batches, and it depends on the amount of transient capacity available in the cluster. When the transient capacity exceeds the maximum limit, vSAN waits for the transient capacity to be freed before proceeding with the reformatting. During this phase, the task might appear to be halted. The health alert will clear and the task will progress when transient capacity is available.

  Workaround: None. The task is working as expected. 

• System VMs cannot be powered-off

  With the release of vSphere Cluster Services (vCLS) in vSphere 7.0 Update 1, a set of system VMs might be placed within the vSAN cluster. These system VMs cannot be powered-off by users. This issue can impact some vSAN workflows, which are documented in the following article: https://kb.vmware.com/s/article/80877

  Workaround: For more information about this issue, refer to KB 80483. 

• vSAN File Service cannot be enabled due to an old vSAN on-disk format version.

  vSAN File Service cannot be enabled with the vSAN on-disk format version earlier than 11.0 (this is the on-disk format version in vSAN 7.0).

  Upgrade the vSAN disk format version before enabling file service.

• Remediate cluster task might fail in large scale cluster due to vSAN health network test issues

  Large scale clusters with more than 16 hosts, intermittent ping failures can occur during host upgrade. These failures can interrupt host remediation in vSphere Life Cycle Manager.

  After remediation pre-check passes, silence alerts for the following vSAN health tests:

  • vSAN: Basic (unicast) connectivity check
  • vSAN: MTU check (ping with large packet size)

  When the remediation task is complete, restore alerts for the vSAN health tests.

• Host failure in hot-plug scenario when drive is reinserted

  During a hot drive removal, VMware native NVMe hot-plug can cause a host failure if the NVMe drive is pulled and reinserted within one minute. This is applicable to both vSphere and vSAN for any new or existing drive reinsertion.

  Workaround: After removing a hot drive, wait for one minute before you reinsert the new or existing drive.

• Cannot place last host in a cluster into maintenance mode, or remove a disk or disk group

  Operations in Full data migration or Ensure accessibility mode might fail without providing guidance to add a new resource, when there is only one host left in the cluster and that host enters maintenance mode. This can also happen when there is only one disk or disk group left in the cluster and that disk or disk group is to be removed.

  Workaround: Before you place the last remaining host in the cluster into maintenance mode with Full data migration or Ensure accessibility mode selected, add another host with the same configuration to the cluster. Before you remove the last remaining disk or disk group in the cluster, add a new disk or disk group with the same configuration and capacity.

• Object reconfiguration workflows might fail due to the lack of capacity if one or more disks or disk groups are almost full

  vSAN resyncs get paused when the disks in non-deduplication clusters or disk groups in deduplication clusters reach a configurable resync pause fullness threshold. This is to avoid filling up the disks with resync I/O. If the disks reach this threshold, vSAN stops reconfiguration workflows, such as EMM, repairs, rebalance, and policy change.

  Workaround: If space is available elsewhere in the cluster, rebalancing the cluster frees up space on the other disks, so that subsequent reconfiguration attempts succeed.

• After recovery from cluster full, VMs can lose HA protection

  In a vSAN cluster that has hosts with disks 100% full, the VMs might have a question pending and hence lose the HA protection. Also, the VMs that had a pending question are not HA protected after recovering from cluster full scenario.

  Workaround: After recovering from vSAN cluster full scenario, perform one of the following actions:

  • Disable and re-enable HA.
  • Reconfigure HA.
  • Power off and power on the VMs.
• Power Off VMs fails with Question Pending

  If a VM has a pending question, you are not allowed to do any VM-related operations until the question is answered.

  Workaround: Try to free the disk space on the relevant volume, and then click Retry.

• When the cluster is full, the IP addresses of VMs either change to IPV6 or become unavailable

  When a vSAN cluster is full with one or more disk groups reaching 100%, there can be a VM pending question that requires user action. If the question is not answered and if the cluster full condition is left unattended, the IP addresses VMs might change to IPv6 or become unavailable. This prevents you from using SSH to access the VMs.  It also prevents you from using the VM console, because the console goes blank after you type root.

  Workaround: None.

• Unable to remove a dedupe enabled disk group after a capacity disk enters PDL state

  When a capacity disk in a dedupe-enabled disk group is removed, or its unique ID changes, or when the device experiences an unrecoverable hardware error, it enters Permanent Device Loss (PDL) state. If you try to remove the disk group, you might see an error message informing you that the action cannot be completed.

  Workaround: Whenever a capacity disk is removed, or its unique ID changes, or when the device experiences an unrecoverable hardware error, wait for a few minutes before trying to remove the disk group.

• vSAN health indicates non-availability related incompliance with failed pending policy

  A policy change request leaves the object health status of vSAN in a non-availability related incompliance state. This is because there might be other scheduled work that is utilizing the requested resources. However, vSAN reschedules this policy request automatically as resources become available.

  Workaround: The vSAN period scan fixes this issue automatically in most cases. However, other work in progress might use up available resources even after the policy change was accepted but not applied. You can add more capacity if the capacity reporting displays a high value.

• In deduplication clusters, reactive rebalancing might not happen when the disks show more than 80% full

  In deduplication clusters, when the disks display more than 80% full on the dashboard, the reactive rebalancing might not start as expected. This is because in deduplication clusters, pending writes and deletes are also considered for calculating the free capacity.

  Workaround: None.

• TRIM/UNMAP commands from Guest OS fail

  If the Guest OS attempts to perform space reclamation during online snapshot consolidation, the TRIM/UNMAP commands fail. This failure keeps space from being reclaimed.

  Workaround: Try to reclaim the space after the online snapshot operation is complete. If subsequent TRIM/UNMAP operations fail, remount the disk.

• Space reclamation from SCSI TRIM/UNMAP is lost when online snapshot consolidation is performed

  Space reclamation achieved from SCSI TRIM/UNMAP commands is lost when you perform online snapshot consolidation. Offline snapshot consolidation does not affect SCSI unmap operation.

  Workaround: Reclaim the space after online snapshot consolidation is complete.

• Host failure when converting data host into witness host

  When you convert a vSAN cluster into a stretched cluster, you must provide a witness host. You can convert a data host into the witness host, but you must use maintenance mode with Full data migration during the process. If you place the host into maintenance mode with Ensure accessibility option, and then configure it as the witness host, the host might fail with a purple diagnostic screen.

  Workaround: Remove the disk group on the witness host and then re-create the disk group.

• Duplicate VM with the same name in vCenter Server when residing host fails during datastore migration

  If a VM is undergoing storage vMotion from vSAN to another datastore, such as NFS, and the host on which it resides encounters a failure on the vSAN network, causing HA failover of the VM, the VM might be duplicated in the vCenter Server. 

  Workaround: Power off the invalid VM and unregister it from the vCenter Server. 

• Reconfiguring an existing stretched cluster under a new vCenter Server causes vSAN to issue a health check warning
  When rebuilding a current stretched cluster under a new vCenter Server, the vSAN cluster health check is red. The following message appears: vSphere cluster members match vSAN cluster members

  Workaround: Use the following procedure to configure the stretched cluster.

  1. Use SSH to log in to the witness host.
  2. Decommission the disks on witness host. Run the following command: esxcli vsan storage remove -s "SSD UUID"
  3. Force the witness host to leave the cluster. Run the following command: esxcli vsan cluster leave
  4. Reconfigure the stretched cluster from the new vCenter Server (Configure > vSAN > Fault Domains & Stretched Cluster). 

   

• Disk format upgrade fails while vSAN resynchronizes large objects
  If the vSAN cluster contains very large objects, the disk format upgrade might fail while the object is resynchronized. You might see the following error message: Failed to convert object(s) on vSAN

  vSAN cannot perform the upgrade until the object is resynchronized. You can check the status of the resynchronization (Monitor > vSAN > Resyncing Components) to verify when the process is complete.

  Workaround: Wait until no resynchronization is pending, then retry the disk format upgrade.

• Cluster consistency health check fails during deep rekey operation
  The deep rekey operation on an encrypted vSAN cluster can take several hours. During the rekey, the following health check might indicate a failure: Cluster configuration consistency. The cluster consistency check does not detect the deep rekey operation, and there might not be a problem.

  Workaround: Retest the vSAN cluster consistency health check after the deep rekey operation is complete.

• vSAN stretched cluster configuration lost after you disable vSAN on a cluster
  If you disable vSAN on a stretched cluster, the stretched cluster configuration is not retained. The stretched cluster, witness host, and fault domain configuration is lost.

  Workaround: Reconfigure the stretched cluster parameters when you re-enable the vSAN cluster.

• Powered off VMs appear as inaccessible during witness host replacement

  When you change a witness host in a stretched cluster, VMs that are powered off appear as inaccessible in the vSphere Web Client for a brief time. After the process is complete, powered off VMs appear as accessible. All running VMs appear as accessible throughout the process.

  Workaround: None. 

• Cannot place hosts in maintenance mode if they have faulty boot media
  vSAN cannot place hosts with faulty boot media into maintenance mode. The task to enter maintenance mode might fail with an internal vSAN error, due to the inability to save configuration changes. You might see log events similar to the following: Lost Connectivity to the device xxx backing the boot filesystem

  Workaround: Remove disk groups manually from each host, using the Full data evacuation option. Then place the host in maintenance mode.

• Health service does not work if vSAN cluster has ESXi hosts with vSphere 6.0 Update 1 or earlier
  The vSAN 6.6 and later health service does not work if the cluster has ESXi hosts running vSphere 6.0 Update 1 or earlier releases.

  Workaround: Do not add ESXi hosts with vSphere 6.0 Update 1 or earlier software to a vSAN 6.6 or later cluster.

• After stretched cluster failover, VMs on the preferred site register alert: Failed to failover

  If the secondary site in a stretched cluster fails, VMs failover to the preferred site. VMs already on the preferred site might register the following alert: Failed to failover. Ignore this alert. It does not impact the behavior of the failover.

  Workaround: None. 

• During network partition, components in the active site appear to be absent
  During a network partition in a vSAN 2 host or stretched cluster, the vSphere Web Client might display a view of the cluster from the perspective of the non-active site. You might see active components in the primary site displayed as absent.

  Workaround: Use RVC commands to query the state of objects in the cluster. For example: vsan.vm_object_info

• Some objects are non-compliant after force repair
  After you perform a force repair, some objects might not be repaired because the ownership of the objects was transferred to a different node during the process. The force repair might be delayed for those objects.

  Workaround: Attempt the force repair operation after all other objects are repaired and resynchronized. You can wait until vSAN repairs the objects.

• When you move a host from one encrypted cluster to another, and then back to the original cluster, the task fails
  When you move a host from an encrypted vSAN cluster to another encrypted vSAN cluster, then move the host back to the original encrypted cluster, the task might fail. You might see the following message: A general system error occurred: Invalid fault. This error occurs because vSAN cannot re-encrypt data on the host using the original encryption key. After a short time, vCenter Server restores the original key on the host, and all unmounted disks in the vSAN cluster are mounted.

  Workaround: Reboot the host and wait for all disks to get mounted.

• Stretched cluster imbalance after a site recovers
  When you recover a failed site in a stretched cluster, sometimes hosts in the failed site are brought back sequentially over a long period of time. vSAN might overuse some hosts when it begins repairing the absent components.

  Workaround: Recover all of the hosts in a failed site together within a short time window.

• VM operations fail due to HA issue with stretched clusters

  Under certain failure scenarios in stretched clusters, certain VM operations such as vMotions or powering on a VM might be impacted. These failures scenarios include a partial or a complete site failure, or the failure of the high speed network between the sites. This problem is caused by the dependency on VMware HA being available for normal operation of stretched cluster sites.

  Workaround: Disable vSphere HA before performing vMotion, VM creation, or powering on VMs. Then re-enable vSphere HA.

• Cannot perform deep rekey if a disk group is unmounted
  Before vSAN performs a deep rekey, it performs a shallow rekey. The shallow rekey fails if an unmounted disk group is present. The deep rekey process cannot begin.

  Workaround: Remount or remove the unmounted disk group.

• Log entries state that firewall configuration has changed
  A new firewall entry appears in the security profile when vSAN encryption is enabled: vsanEncryption. This rule controls how hosts communicate directly to the KMS. When it is triggered, log entries are added to /var/log/vobd.log. You might see the following messages:

  Firewall configuration has changed. Operation 'addIP4' for rule set vsanEncryption succeeded.
  Firewall configuration has changed. Operation 'removeIP4' for rule set vsanEncryption succeeded.

  These messages can be ignored.

  Workaround: None. 

• HA failover does not occur after setting Traffic Type option on a vmknic to support witness traffic
  If you set the traffic type option on a vmknic to support witness traffic, vSphere HA does not automatically discover the new setting. You must manually disable and then re-enable HA so it can discover the vmknic. If you configure the vmknic and the vSAN cluster first, and then enable HA on the cluster, it does discover the vmknic.

  Workaround: Manually disable vSphere HA on the cluster, and then re-enable it.

• iSCSI MCS is not supported

  vSAN iSCSI target service does not support Multiple Connections per Session (MCS).

  Workaround: None. 

• Any iSCSI initiator can discover iSCSI targets
  vSAN iSCSI target service allows any initiator on the network to discover iSCSI targets.

  Workaround: You can isolate your ESXi hosts from iSCSI initiators by placing them on separate VLANs.

• After resolving network partition, some VM operations on linked clone VMs might fail
  Some VM operations on linked clone VMs that are not producing I/O inside the guest operating system might fail. The operations that might fail include taking snapshots and suspending the VMs. This problem can occur after a network partition is resolved, if the parent base VM's namespace is not yet accessible. When the parent VM's namespace becomes accessible, HA is not notified to power on the VM.

  Workaround: Power cycle VMs that are not actively running I/O operations.

• Cannot place a witness host in Maintenance Mode
  When you attempt to place a witness host in Maintenance Mode, the host remains in the current state and you see the following notification: A specified parameter was not correct.

  Workaround: When placing a witness host in Maintenance Mode, choose the No data migration option.

• Moving the witness host into and then out of a stretched cluster leaves the cluster in a misconfigured state
  If you place the witness host in a vSAN-enabled vCenter cluster, an alarm notifies you that the witness host cannot reside in the cluster. But if you move the witness host out of the cluster, the cluster remains in a misconfigured state.

  Workaround: Move the witness host out of the vSAN stretched cluster, and reconfigure the stretched cluster. For more information, see Knowledge Base article 2130587.

• When a network partition occurs in a cluster which has an HA heartbeat datastore, VMs are not restarted on the other data site
  When the preferred or secondary site in a vSAN cluster loses its network connection to the other sites, VMs running on the site that loses network connectivity are not restarted on the other data site, and the following error might appear: vSphere HA virtual machine HA failover failed.

  This is expected behavior for vSAN clusters.

  Workaround: Do not select HA heartbeat datastore while configuring vSphere HA on the cluster.

• Unmounted vSAN disks and disk groups displayed as mounted in the vSphere Web Client Operational Status field

  After the vSAN disks or disk groups are unmounted by either running the esxcli vsan storage disk group unmount command or by the vSAN Device Monitor service when disks show persistently high latencies, the vSphere Web Client incorrectly displays the Operational Status field as mounted.

  Workaround: Use the Health field to verify disk status, instead of the Operational Status field.