Steam validating files every time
Please restart Steam and then repeat the downloading/upgrading.If the Steam disk write error persists, restart your computer then.
In this case, it is better for you to back up data on the drive as soon as possible and then replace the drive.Luckily, Mini Tool Partition Wizard Free is also capable of doing this work. At the disk map error, select the hard drive which has Steam installed and choose Copy Disk from the left action panel. Select a target disk to save all data on the source disk.Be aware that all data on the selected target disk will be cleaned for a successful clone.Guess this solution might be also useful to the similar games updating. When a disk is write-protected, you're unable to modify it like formatting and writing.This is another possible reason for the Steam disk write error.