Before updating to mavericks
Can not afford to lose any info(Mac Book Pro Retina 1TB SSD, 16 GB RAM 13 inch with touchbar).That is why we have so many online forums set up to fix Mac Book Pro problems- both hardware as well as software problems.This also holds true for later versions of the operating system.
When you purchase OS X Mavericks from the Mac App Store, the installer will be downloaded to your Mac and placed in the Applications folder.Not only you should have a backup before every update (minor or major) but you should have regular backups anyways- at least once a week, if not daily. I also suggest and highly recommend that you subscribe to an online backup service(needs a good internet speed though). Upgrading from a previous version of OS X is the most common method of installing OS X Mavericks.I highly recommend having both a Time Machine or other conventional backup of your Mac, as well as a clone of your startup drive.Some may consider this a bit of overkill, but I like having a very reliable safety net.