Microsoft will release some time during the week of May 4 its second technical previews of what execs are officially christening Windows Server 2016 and System Center 2016.

Update: It looks like the second preview of Windows Server 2016 is available for download today, May 4. And Systems Center 2016 preview 2 is now on tap for next week, company officials disclosed during the Ignite keynote this morning.

These previews are the first new builds of these next-generation server products, which are due to ship in final form in calendar 2016, that Microsoft has made publicly available. The first public test builds of these servers were released on October 1, 2014.

Microsoft officials announced more details about what's coming in these second previews during the first day of the company's Ignite conference in Chicago on May 4.

The second preview of Windows Server 2016 will include for the first time Nano Server, which is a new way of deploying Windows Server in a very stripped-down, headless form.

The second Windows Server 2016 preview also includes support for rolling upgrades for Hyper-V and Storage Clusters and compute resiliency, which will enable virtual machines (VMs) to continue running even if compute-cluster fabric service fails. Storage Replica -- a synchronous storage replication feature for backup and disaster recovery -- will be in this second preview, as well.

The new Windows Server Container and Hyper-V Container functionality that Microsoft is building into Windows Server 2016 won't be available in preview form until the next technical preview, which will be available some time this summer, Microsoft officials said. The same is true of the Service Fabric that Microsoft is building into both Azure and Windows Server. That technology is coming in a future preview of Windows Server 2016, according to Microsoft officials.

New features in System Center 2016 technical preview 2 include:

Improved Linux management, including Desired State Configuration (DSC) support, native SSH support, and improved LAMP stack monitoring.

Software Defined Datacenter management, including mixed mode cluster upgrades, enhanced Scale-Out File Server (SOFS) management, and deployment of software-defined networking (SDN) at scale.

New monitoring capabilities for Azure, Office365, SQL Server and Exchange.

Microsoft officials said to expect both Windows Server 2016 and System Center 2016 to ship in calendar 2016. The System Center Configuration Manager piece of Microsoft's management suite will be out in 2015, alongside Windows 10, however.

In related news, Microsoft officials said today a public preview of the next version of SQL Server, known as SQL Server 2016, is coming later this summer.