It is important to set max degree of parallelism (MAXDOP) to 1 for SQL Server instances that host SharePoint Server 2013 databases to ensure that each request is served by a single SQL Server process.
Default setting for SQL Server 2008 R2 is 0, it was optional for SharePoint 2010 and recommendation was to set to 1. It is now required for SharePoint 2013, SharePoint Products Configuration Wizard (PSCONFIG / PSCONFIGUI) would fail if MDOP is 0 in multi-server farm. Please note that if you are installing SharePoint on single server farm with SQL Server on same machine, SharePoint product configuration wizard will set MDOP to 1 automatically but it would fail in multi-server SharePoint farm – http://technet.microsoft.com/en-us/library/ms189094(v=sql.105) & http://blogs.technet.com/b/sqlpfeil/archive/2012/02/01/four-tips-for-sql-tuning-for-sharepoint-part-1.aspx
Here is the screenshot of default setting for SQL Server 2008 R2. You can validate/set Max Degree of Parallelism from Advance tab of SQL Server instance properties using SQL Server Management Studio. You must change this setting to 1 to ensure SharePoint Installation and Configuration process succeeds in multi-server SharePoint farm.