When data is imported into a Tencent Cloud-hosted MongoDB instance, the space it occupies may appear smaller than that of a self-built MongoDB deployment due to several factors:
Storage Engine Optimization: Tencent Cloud's MongoDB service uses optimized storage engines (like WiredTiger) with built-in compression, reducing the physical storage footprint. Self-built MongoDB might not always have the same compression settings enabled or tuned properly.
Data Fragmentation Handling: Tencent Cloud's managed service automatically handles data fragmentation and compaction, whereas a self-built MongoDB may accumulate fragmented data over time, leading to inefficient space usage.
Pre-allocated Storage Management: In self-built MongoDB, storage is often pre-allocated (e.g., fixed-size data files), which can lead to unused space. Tencent Cloud's MongoDB dynamically manages storage allocation, reducing wasted space.
Replication and Backup Overhead: Self-built MongoDB may include additional copies (e.g., for replication or backups) that consume extra space, while Tencent Cloud's service abstracts and optimizes these processes.
Example: If you import 100GB of data into a self-built MongoDB with default settings, it might occupy 120GB due to fragmentation and lack of compression. In contrast, Tencent Cloud's MongoDB, with WiredTiger compression and automatic compaction, might store the same data in only 80GB.
For such scenarios, Tencent Cloud's MongoDB service provides automated storage optimization, ensuring efficient space utilization.