So, Redis is a piece of software and as such it requires RAM to operate. But Redis is not just any software, it is an in-memory database, which means that every piece of data Redis manages is kept in RAM too.

How much RAM does Redis use?

Production environment

Item Minimum Requirements Recommended
RAM* per node 15GB >=30GB
Ephemeral Storage RAM x 2 >= RAM x 4
Persistent Storage RAM x 3 In-memory >= RAM x 6 (except for extreme ‘write’ scenarios); Redis on Flash >= (RAM + Flash) x 5.
Network 1G >=10G

Does Redis use RAM or SSD?


Long story short, REDIS allows you to store key-value pairs on your RAM. Since accessing RAM is 150,000 times faster than accessing a disk, and 500 times faster than accessing SSD, it means speed. But, we are already using RAM for most of our operations!

Is Redis persistent or in-memory?

Data size is predictable and limited: Redis data is always kept in memory, even when backup to disk, and RAM is much more expensive than Hard drive (the cost of a 500GB RAM cluster in any Cloud provide environment will convince you of that).

Is Redis memory efficient?

Basically it is possible to model a plain key-value store using Redis where values can just be just strings, that is not just more memory efficient than Redis plain keys but also much more memory efficient than memcached.

Why is Redis using so much memory?

Hence, the main culprit for excessive memory usage with Redis is application behaviour. Your application may be storing unnecessary data that does not benefit from being in Redis, or even completely redundant data, i.e, data that’s never used for any purpose, as this user was.

Is Redis faster than SSD?

Our benchmark shows that Redis is faster in all three operations than file system-based storage (NVMe SSDs) or storage in the MySQL database.

What happens if Redis runs out of memory?

If this limit is reached Redis will start to reply with an error to write commands (but will continue to accept read-only commands), or you can configure it to evict keys when the max memory limit is reached in the case you are using Redis for caching.

How fast is Redis?

Introduction to Redis

Actually, Redis is an advanced key-value store. It is super fast with amazingly high throughput, as it can perform approximately 110000 SETs per second, about 81000 GETs per second. It also supports a very rich set of data types to store.

Why is Redis cache slow?

Inadequate hardware (network, memory, CPU) Software based virtualization (Xen on low-end hardware for instance) Not enough memory, generating swapping at the OS level. Too many O(n) operations (like KEYS) executed in the single-threaded engine.

What should you not use Redis for?

7 Redis Worst Practices

  1. No password. …
  2. KEYS. …
  3. Numbered databases/SELECT. …
  4. Unbounded Returns with HGETALL, LRANGE, SMEMBERS, and ZRANGE. …
  5. One request per connection. …
  6. Hot keys. …
  7. Running ephemeral Redis as a primary database.

Does Redis compress?

By default, Redis does not compress values it stores (read more here), so any size-reduction would have to be performed on the application side first. We found that the storage and network throughput savings achieved through any of our manual compression options were worth the additional processing time.

How do I optimize Redis?

Performance Tuning for Redis

  1. Verify your hosts’ health by looking at server data.
  2. Ensure that your virtualization works fine by analyzing virtual machine metrics.
  3. Optimize database access with application data.
  4. Analyze the network impact of database communication with network data.

How big can a Redis value be?

512 MiB

All string values are limited to 512 MiB. This is the size limit you probably care most about. EDIT: Because keys in Redis are strings, the maximum key size is 512 MiB. The maximum number of keys is 2^32 – 1 = 4,294,967,295.

How much data can you store in Redis?

512 megabytes

You can store up to 512 megabytes in a Redis string. It can store any type of data, like text, integers, floats, videos, images, or audio files. In this example, SET and GET are Redis commands, which we will discuss later.

How is Redis so fast?

Built for Speed & Languages

To work as quickly as it does, Redis uses a dataset that is in-memory. In order to maintain the data, you can save it to disk occasionally or attach all commands to a log. In fact, you don’t always want persistence, so you can turn it off if you’re using it to temporarily cache.

Can Redis be used for long term storage?

You can have none, partial or full persistence of your data on Redis. The best decision will be driven by the project’s technical and business needs. According to the Redis documentation about persistence you can set up your instance to save data into disk from time to time or on each query, in a nutshell.

Is Redis cache free?

I found Redis cache is open source and free to download.

Is Redis faster than MongoDB?

MongoDB is schemaless, which means that the database does not have a fixed data structure. This means that as the data stored in the database gets larger and larger, MongoDB is able to operate much faster than Redis. Redis is only significantly faster when the stored data is relatively small in size.

Is Redis in-memory cache?

Both Redis and Memcached are in-memory, open-source data stores. Memcached, a high-performance distributed memory cache service, is designed for simplicity while Redis offers a rich set of features that make it effective for a wide range of use cases.

Which is faster Redis or Memcached?

Redis uses a single core and shows better performance than Memcached in storing small datasets when measured in terms of cores. Memcached implements a multi-threaded architecture by utilizing multiple cores. Therefore, for storing larger datasets, Memcached can perform better than Redis.

Is Redis multithreaded?

Redis is, mostly, a single-threaded server from the POV of commands execution (actually modern versions of Redis use threads for different things). It is not designed to benefit from multiple CPU cores. People are supposed to launch several Redis instances to scale out on several cores if needed.

Is Redis volatile?

Data in Redis is volatile. It lives in system memory, so data in Redis must be synced with a longer-term storage mechanism if that data should be saved.

What is better than Redis?

Top Alternatives to Redis

  • Memcached. Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering. …
  • MongoDB. …
  • RabbitMQ. …
  • Hazelcast. …
  • Cassandra. …
  • MySQL. …
  • SQLite. …
  • Aerospike.

Which is faster Redis or MySQL?

In terms of the efficiency of updating databases, Redis is superior to MySQL while SQLite is slowest. However, in terms of the efficiency of querying from databases, SQLite seems to be about ten times faster than Redis and MySQL.

Is Redis faster than NoSQL?

Redis: Speed: Redis is faster than MongoDB because it’s an in-memory database. RAM: Redis uses more RAM than MongoDB for non-trivial data sets. Scalability: MongoDB scales better than Redis.