File Backup Software versus File Synchronization Tools
File synchronization software differs from file backup software in that file synchronization makes plain copies of file and folders to another location, such as an external drive, whereas file backup does much more. File backup software usually offers compression, deduplication, encryption, and versioning. In addition, file backup software caters to the needs of IT admins and provides additional management tools to manage backups and find and restore files easier when large volumes are involved.
Large file volumes also set apart scripts and file sync tools from professional backup software. Most file synchronization tools crash when the file / folder structure is deep and very long.
Error potential: File backups are done by reading the original and writing it to another media
Each time a full backup is taken, all data is read from the original drive, perhaps processed (compressed / encrypted), and then written to the target drive or media.
File backup software tools are best used to do this on a regular basis; however, one needs to be aware of the following risks:
Bit rot: bits on the disk and even inside the computer’s RAM memory may get ‘stuck’ or fail to activate. This phenomenon is known as bit rot. Basically this means the data being read or written may become corrupted when the process involves a bit defect. This can happen on the source disk, inside the computer’s main hardware, or on the target media. It may also be caused by external interference or be a result of wear-and-tear on the drive, such as with SSD drives.
Viruses and malware: viruses can be very hard to spot and only a small percentage of viruses and malware are actually caught by anti-virus scanners. Viruses can be so devious, some a capable of interfering with disk read and write operations, so that different file contents are sent to backup applications and even the operating system itself. Viruses, hence, may be a major source of data corruption. Also see this article.
Bad disk sectors: many people don’t realize it, but digital storage media has a limited lifespan and also suffers from wear-and-tear as all other physical objects. At some point in time, one or more bits may fail inside a drive, or inside the computer’s RAM or CPU. This may happen, ergo, to the original or the target. If the original is affected, the file ends up corrupted in the backup folder. If the defect is in the backup media, the backup is corrupt but the original is fine. In that case if you have a second backup, you may be able to recover the file successfully.
RAM defects: What does RAM have to do with file backup software? Well, all read, write, and compression operations are done using RAM. If there’s a defect in RAM, the file contents may be loaded to a defected area where the contents of the files are being changed without notice. If you are lucky, the PC may crash one day and thus give you a hint that something is wrong; however, we’ve seen plenty of servers running for years with RAM issues that went unnoticed….and corrupted quite a few files before the real issue was uncovered months later.
File Versioning and File Backup Versioning
Good file backup software tools offer file versioning. This basically means the backup solution offers a way to go back in time and restore previous contents of the same file. Say you write a novel and the backup tool backs up the Word document every hour. Because you’re paranoid, you want to keep every single copy—just in case. After weeks of working on your novel, you realize that some time a week or so ago you deleted a section. Now you want it back. File versioning is exactly what is needed to give you back an earlier version of your novel so you can copy those sections out and back to your current Word document.
File Backup Deduplication, aka Source Deduplication
File backup deduplication refers to a technique to save storage space by removing file contents that haven’t changed since the last file backup cycle. Say you write a novel and it’s being backed up hourly. As you add more paragraphs to the end, the rest of your novel remains the same from hour to hour.
A good backup software tool recognizes that contents changed only partially and backs up only the difference. When very large files are being backed up, this is a gigantic improvement. Virtual machine backups and database backups, for example, are greatly reduced in size, as much as 95% or more. There are some file systems that support deduplication on NTFS at the source, but this technology has quite a few limitations.
File Backup Compression
Professional backup software provides several means of compressing data and files. Depending on the nature of files, some files compress better than others. For example, text documents compress very well, whereas videos and images don’t compress at all when attempting a lossless file backup compression. A great file backup tool will possess the ability to skip compression based on file type.
Backup of Very Long Path Names
Many users are surprised when a backup run by a freeware file sync tool suddenly stops working and generates errors. Many of those tools weren’t made correctly and cannot handle very long file names and paths. In Microsoft Windows, file paths may reach over 32,000 letters. BackupChain handles files with very long path names correctly.
Incompatible file systems, file system limitations
When backing up files, make sure the backup media supports the same kind of file system as the source. On Windows, this is usually NTFS. As mentioned above, NTFS supports very long file names of over 32,000 characters and huge file sizes in terabytes and more. Many older or Linux-based file systems don’t support the same kind of file names (and characters), file sizes, and so on. There are more limitations in other file systems, too, such as the maximum number of files per folder, and so on.
These incompatibilities can become an issue on business file servers.
For that reason we recommend that NTFS is used throughout on your backup media as well.
Full / incremental / differential backups
As there are many different backup software tools out there, there are also different definitions for full, incremental, and differential backup.
The reality is that more of the content on computer hard drives doesn’t change from day to day.
Most files don’t change at all. Server-grade file backup software will therefore quickly investigate whether a file has changed and skip it. Stale files shouldn’t require repeated backup.
Incremental backups refer to the last backup done; i.e., the comparison is done to the previous backup on file.
Differential backups compare the current file structure to the last full backup.
Note that when using deduplication, these terms are defined similarly but refer to the file contents. Incremental file deduplication backs up the content change of a file when compared to the previous contents backed up.
Backup of ACL and folder and file access permissions
On business file servers it’s common to assign different access rights to files and folders depending on user account or user group accounts. These access control lists (ACL) and folder and file access permissions should also be backed up when file synchronization or file backups are taken.
There are some circumstances where the admin may want to strip these access rights off and back up only file contents. For example, you may want to delete ACLs when those user accounts and groups who once owned the files have been deleted.
In addition, when using ACLs you want make sure the file backup application uses a user account that is granted full access to the folder structure; otherwise, it may need to skip over sections it can’t access.
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