Tair ESSD/SSD-based instances store data on ESSDs (Enhanced SSDs) or local SSDs instead of volatile memory, delivering large-capacity, persistent database storage at up to 85% lower cost than Redis Open-Source Edition instances. These instances are compatible with most Redis 6.0 data structures and commands, making them a drop-in option for workloads with warm and cold data patterns.
Background
Redis stores all data in volatile memory. As your data volume grows, this creates three problems:
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Cost: Rarely accessed data still occupies expensive memory, making in-memory storage less cost-effective over time.
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Persistence: You need to integrate additional databases or storage systems to handle data durability.
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Capacity: Standalone instances and cluster size limits cap how much data you can store.
ESSD/SSD-based instances address all three by using disk-based storage with the TairDB storage engine, which combines disks and memory to provide an optimal balance between data persistence and quick access to data.
Key features
| Feature | Details |
|---|---|
| Compatibility | Compatible with most data structures and commands of Redis 6.0. See Limits on commands supported by Tair. |
| Cost | Up to 85% lower cost compared with Redis Open-Source Edition instances. |
| Performance | Approximately 60% of the throughput of Redis Open-Source Edition instances. See performance whitepapers for ESSD-based and SSD-based instances. |
| Capacity | Storage capacity can reach hundreds of terabytes. |
| Data reliability | Data is persisted to ESSDs or local SSDs, eliminating the risk of data loss from memory volatility. |
| Replication | Supports semi-synchronous replication mode in addition to the default asynchronous mode. |
| Storage engine | Uses the TairDB storage engine developed by Alibaba Cloud, which combines disk and memory to balance data persistence with access speed. |
Use cases
ESSD/SSD-based instances are well-suited for workloads where a small fraction of the dataset is frequently accessed and the rest is accessed infrequently. Typical scenarios include:
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Warm and cold data storage: Large datasets where only a portion of data is accessed regularly and the rest is seldom read. Disk-based storage eliminates the cost of holding rarely accessed data in memory.
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High-capacity archives: Datasets that exceed what a standalone in-memory instance can hold, requiring hundreds of terabytes of persistent storage.
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Redis-compatible migrations: Workloads that need Redis 6.0 API compatibility combined with disk-backed persistence, without additional integration work.
ESSD-based vs SSD-based instances
Tair offers two sub-types within this series. The right choice depends on your architecture and capacity requirements.
| Item | ESSD-based instance | SSD-based instance |
|---|---|---|
| Storage medium | ESSDs at performance levels PL1, PL2, and PL3. PL3 outperforms PL2 and PL1. | Local SSDs |
| Instance architecture | Standard architecture only | Standard and cluster architectures |
| Storage capacity | Custom, in increments of 10 GB | Fixed capacity options |
| Backup and restoration | Snapshot-based backup of cloud disks — faster backup and restoration speeds | Physical backup; speed varies by data volume |
| Cost | Higher than SSD-based instances of comparable specifications | More cost-effective than ESSD-based instances of the same specifications |
Choose ESSD-based instances if you need custom storage capacity increments, faster snapshot-based backup and restoration, or plan to scale storage independently of compute.
Choose SSD-based instances if you need cluster architecture support or want the most cost-effective option at a fixed capacity tier.
Limitations
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Command compatibility: Not all Redis 6.0 commands are supported. Review the full list at Limits on commands supported by Tair.
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Architecture: ESSD-based instances support only the standard architecture. Cluster architecture is available only on SSD-based instances.
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Performance trade-off: Disk-based storage delivers approximately 60% of the throughput of Redis Open-Source Edition instances. Workloads that require sub-millisecond latency across the full dataset are better served by memory-optimized instances.
Instance specifications
For available instance types and capacity options, see ESSD/SSD-based instance specifications.
FAQ
What storage engine and Redis version do ESSD/SSD-based instances use?
ESSD/SSD-based instances run the TairDB storage engine, developed in-house by Alibaba Cloud, and are compatible with Redis 6.0. For the full list of supported commands, see Limits on commands supported by Tair.