Upgrade SQL Server in SharePoint 2010 Farm

Hello All,

I have a  SharePoint 2010 farm running with Microsoft SQL Server 2008 (SP3) - 10.0.5500.0 (X64) in the back end. I would like to upgrade SQL to SQL 2008 R2 without any impact to SHarePoint farm. Please suggest what would be the best approach.

Thanks

Kishore