Overview
If you are using the Windows operating system and your backup status isn't reaching 100%, one possible cause could be that you are backing up file paths and names that exceed a 255-260 character limit. This article provides a technical explanation for this issue and a recommended solution.
Affects
The CrashPlan app running on Windows (all versions, x86 and x64)
Before you begin
If you haven't done so already, you may want to start by reading our Windows solutions guide for Unable to Back Up X Files issues.
Under the hood
Microsoft has a core set of application programming interfaces (APIs) that programmers can use to interact with applications in the Windows operating system. These programming interfaces are often referred to as the Windows API. The Windows API imposes a maximum filename length such that a filename, including the file path to get to the file, can't exceed 255-260 characters.
However, because this is a limitation of the Windows API and not the file system used on the majority of Windows installations (NTFS), some programs can create filenames that violate this limit.
When the CrashPlan app attempts to read these files for backup, it fails because Windows doesn't know how to handle the file. When this occurs, the following error message displays in the CrashPlan app service.log:
WARN W196815609_BQTodoWkr 2.os.win.metadata.WindowsMetadataHandler] Problem getting named streams for file={filename}, e=java.io.FileNotFoundException: Could not open file...handleValue is invalid {filename}Diagnosing
Symptoms of this issue include:
- Your backup never reaches 100%
- The CrashPlan app is running but certain files stay on the backup to-do list
It can be difficult to correct this issue. If you try to rename, move, or delete the file in Windows, you may receive the following messages:
Recommended solution
Since you are not able to move the files using Windows Explorer, you must use the subst command to shorten the file path for the file(s).
The simplest way to fix this is to:
- Substitute the folder that has a long file path with a drive letter (thereby shortening the overall character count for the files contained in the folder)
- Copy or move the files out of the folder into another folder that won't violate the limit
- Delete the mapped folder
You can do this using the method described below.
Use the subst command to assign a drive letter to a specific folder
You can substitute a specific folder path with a drive letter using the Windows Command Prompt and the subst command. The command follows the format:
subst <driveletter> <folder path>
For example, if you wanted to replace the folder path C:\Example\File\Path with the drive letter Y, you would enter:
subst Y: C:\Example\File\Path
Now the Y:drive is "mapped" directly to the folder. Since you have substituted most of the long file path with Y:, it no longer violates the character limit. You can now move the files out of this folder to a folder with a shorter file path.
After you move the files, you can delete the virtual drive by running the subst command with the /d parameter. To delete the Y: drive created in the example above, enter:
subst Y: /d