It's incredibly sad how many administrators only care about security updates when it's on a news!
The rest of us have installed these patches two months ago, when they were released. Therefore, we were sleeping well during the whole weekend. The SMB vulnerability has existed all this time, and the patch is released for the vulnerability, not for the WannaCry ransomware attack exploiting it.
You are running out of space, but security updates are the last you would like to miss for saving it. Configure your system for automatic updates. You could remove something less vital, move something to another partition/drive, or simply upgrade your hardware. Even upgrading to a larger hard drive is a minor investment compared to costs caused by recovering from an attack.
Windows Small Business Server 2011 Standard is based on the Windows Server 2008 R2, so the 2008 R2 section on MS17-010 is the correct information. Instead of direct patch for only this problem, Microsoft has simplified servicing models and currently releases a Monthly Rollup addressing both security and reliability issues and Security-only update that only include new security patches.
Historically, we have released individual patches for these platforms,
which allowed you to be selective with the updates you deployed. This
resulted in fragmentation where different PCs could have a different
set of updates installed leading to multiple potential problems. - -
The new rollup model gives you fewer updates to manage, greater
predictability, and higher quality updates.
So, the Security Only update for 2008 R2 is perfectly adequate for addressing this particular problem.