Redis®*: Sizing your service

This documentation is part of the Vector search and RAG guide. You can view the complete guide here: Semantic search, recommendations, and retrieval-augmented generation with Redis.

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Vectors are stored in memory. You can estimate memory requirements with the following formula:

numberOfVectors x dimensions x 4 bytes, plus about 30–50% extra for the HNSW graph.

For example, one million vectors of 1536 dimensions use about 6 GB for the raw vectors. A 20 GB plan is a comfortable starting point for this scale. You can reduce memory usage by:

• Using a smaller model. For example, a 768-dimension model cuts memory usage in half compared to a 1536-dimension model.
• Storing as FLOAT16 instead of FLOAT32 if your model supports it, which halves the space again.

You can monitor actual usage with FT.INFO chunksIndex and the used_memory metric in your Prometheus monitoring. If your needs increase, upgrading your plan is straightforward and can be done directly from your dashboard.