I have noticed that servers in my SharePoint 2013 farm are showing statuses like 'Installation Required' or 'Upgrade Blocked'.
When you install the SharePoint (CU) updates on one of SP server, we see the Installation required and upgrade blocked in the status of servers under the system settings in CA.
Installation Required: The server still not yet installed with the same CU that already installed in other servers in the farm.
Upgrade Blocked : The server is blocked from upgrade as they are on latest CU than other servers in the Farm. Current Server is installed with latest CU and it will remained blocked until all the other SP servers in the farm are installed with the same version.
Sharepoint 2013 Upgrade Required
Upgrading SharePoint 2013 To: SharePoint 2013 SP1 40. Install SharePoint 2013 service-pack 1 on all servers. Install SharePoint 2013 Language pack service pack 1 on all servers 3. Complete the upgrade with psconfig/config-wizard to complete on all servers 4. Install Windows 2012 R2 on all servers Alternative 1: 41. SHAREPOINT 2013 UPGRADE PROCESS RUN SITE COLLECTION HEALTH CHECKS UPGRADE A2 SITE COLLECTION. Configure email settings, farm-level security and permission settings, blocked file types, usage and health data collection settings, and diagnostic logging settings. Alternate access mappings Authentication providers. Upgrade Blocked: The server is blocked from upgrade. Current Server is installed with latest CU and it will remained blocked until all the SP servers in the farm are installed with the same version. Hope it helps 😛.