The CrashPlan app analyzes, compresses, and encrypts your data before sending it to your backup destinations. This article describes how the compression portion of this process is able to increase the efficiency of your backup while still preserving your ability to restore the files to their original state.
What is data compression?
Data compression is the process of reducing file size by encoding the data in a more efficient way. There are many algorithms that can be used to compress and decompress data, which fall in to two categories: lossless, and lossy (used to make MP3s and other media smaller). The CrashPlan app losslessly compresses your data before sending it for backup.
How compression helps your backup
When the CrashPlan app identifies new or changed data in a file, it breaks the data into blocks and compresses each block. The smaller file size increases your effective transfer rate, which makes both backing up and restoring the files faster.
By reducing the file size, compression also reduces the amount of storage space needed at the destination. Between compression and de-duplication, CrashPlan can save a significant amount of disk space. However, data savings can vary greatly based on the type of files being backed up. For example, text documents compress extremely well, but movies do not. Typically, we observe 10-30% savings in disk space as a result of compression and de-duplication.
Does compression harm my data?
The CrashPlan app uses only lossless compression when backing up your data, so your data can be restored to the state that it was in prior to being backed up. This differs from lossy compression:
- Lossless compression reduces file size by identifying and eliminating any redundant data within the file and minimizing wasted space. No data is lost in lossless compression.
- Lossy compression uses partial data discarding to represent the content being encoded. Discarding the data reduces the quality of images, videos, and music. Using this compression type reduces the size of the file by discarding some details of the file that were in the original, such as reducing the number of colors displayed in an image.