In order to back up any file, SpiderOak ONE or Groups must make an encrypted copy of it which is temporarily held on your hard disk. For example, imagine you have a 10 GB file that you have selected for backup. The application will make a temporary copy of it, so you will need at least 10 GB of free disk space to accommodate this. The application will then encrypt the copy and upload it. The temporary copy is retained until our servers notify the program that the transaction has completed. After that, the temporary file will be removed, freeing the 10 GB of disk space that had been used.
For additional information on application data space use and tips on possibly reducing its size, see Reducing the Size of the Application Data Folder.