SAS outlines the support of virtual environments in the SAS^® Product Support for Virtualization Environments policy document. All SAS tiers are supported in a virtual environment. However, not all features provided by a third-party vendor's virtualization software can be employed in an active SAS deployment.

VMware VMotion

The use of VMware VMotion to dynamically move a running virtual machine (VM) where SAS processes are active is known to cause issues and should be avoided. This is partly due to time-critical inter-process communications in the SAS environment. In SAS^®9, issues are typically seen, but not confined to the metadata and middle-tier (web) tiers. Most shared file systems that are used by SAS^® Grid deployments do not allow VMotion without removing nodes from the file system quorum (IBM Spectrum Scale, Red Hat GFS2, and so on). Other VMotion tasks such as patching and software updates can be scheduled with no activity on the host on an automated basis.

The above issues also apply to active VMs in SAS^® Viya^® deployments. In addition, stateful services such as Postgres and RabbitMQ maintain a quorum with other systems. They will be disrupted and stopped with an unplanned VMotion move. The documentation for Postgres and RabbitMQ specifies that you should not use VMotion with their host members.

If a SAS Server in a multi-machine deployment needs to be moved by VMotion, it is best done in a planned maintenance window. It is best to quiesce all activity on the SAS VM, remove it from any cluster quorum, move it, and then rejoin it to quorum. This process includes SAS Viya, shared file system memberships, and so on.

VM Snapshots

You also should not take VM Snapshots on SAS deployment VMs with active SAS processes. The locks placed by the ESXi hypervisor interfere with running jobs, inter-processes communication, and quorum establishment. A snapshot of a VM can be safely performed when the host is quiesced and removed from quorum.   

Operating System and Release Information