Understanding the Deletion Process: What Actually Happens When You Permanently Delete a File Using Shift Delete

When you permanently delete a file on a computer using a command like Shift Delete, several processes occur at the filesystem level. This article delves into the detailed steps of what happens during a file deletion, including the interactions with the file system, data removal, file recovery implications, and differences between HDD and SSD drives.

The File System Interaction

When you delete a file, the following file system actions take place:

File Allocation Table Update: The file system, such as NTFS, FAT32, or ext4, maintains a table that tracks where files are stored on the disk. When a file is deleted, the system marks the space occupied by that file as available for new data. This marking is achieved by updating the file allocation table, FAT, or similar structures. Inode Update: In certain file systems like ext4, the inode associated with the file is updated to indicate that the file is no longer accessible.

Data Removal and Recovery Implications

The actual data remains on the disk until it is overwritten. Here's what happens after you delete a file:

Logical Deletion: The file is logically removed from the directory listing, meaning the operating system no longer recognizes it as a file that can be accessed. Physical Data: The original data is still present on the disk until the storage space is reused. This means that it can potentially be recovered using specialized software unless it has been overwritten.

Tools such as recovery software can often restore deleted files if they have not been replaced. However, for sensitive data, simply deleting files with Shift Delete is not sufficient for secure deletion. Specialized tools that overwrite the data multiple times are necessary to prevent recovery.

SSD vs. HDD

The deletion process and recovery implications vary between traditional hard drives (HDDs) and solid-state drives (SSDs):

Hard Disk Drives (HDDs): On traditional HDDs, the above processes apply directly, and the data remains on the disk until it is overwritten. Solid-State Drives (SSDs): SSDs use a different technology involving TRIM commands. When a file is deleted, the SSD may immediately mark the space as free and erase the data in the background to maintain performance. This makes recovery much more difficult.

Summary

In summary, when you permanently delete a file, the file system updates its metadata to indicate that the space is available for new data. However, the actual data remains on the disk until it is overwritten. For secure deletion, specialized methods are necessary to ensure that the data cannot be recovered.