What is the difference between Qtier and SSD Cache?
Last modified date:
2021-10-15
Applicable Products：
- Storage & Snapshot
If you are considering installing SSDs into your NAS, you may be wondering which configuration may be best suited for your use. Below table compares the pros and cons of each of the configurations:
| Qtier Storage Pool | SSD Cache | All-SSD Storage Pool | |
|---|---|---|---|
| Total file storage space | High (SSDs + HDDs) | Moderate (HDDs only) | Low (SSDs only) |
| Maximum SSD capacity | No limit | Up to 4 TB depending on installed memory | No limit |
| SSD expansion | Expand as needed | Limited by available memory | Expand as needed |
| Applicable storage | Thick volumes, thin volumes and block-based LUNs in the pool | All volumes and LUNs on the NAS | Volumes and LUNs created on the SSDs |
| Data migration | Scheduled or when NAS load is low | Automatic | No migration required |
| Data migration method | QTS writes incoming data to the SSD tier and moves data to different tiers based on access frequency. | Write cache: QTS writes incoming data to the SSD cache and then flushes the cache to disk periodically. Read cache: QTS copies data to the cache as it is accessed. | No migration required |
| Recommended use cases | Total SSD capacity is high I/O is predictable The storage pool only occasionally experiences periods of intense random I/O access | I/O is unpredictable and frequently happens in random bursts Home usage, where the NAS will be used for a large range of different applications | Applications require consistent intensive random read-write access |
| Usage examples | File server, web server, email servers, basic database services (With Qtier IO Aware) | Video editing, virtualization | Business critical database or other application |
