Memcached or redis for image storage

Memcached or redis is recently used as an image application for image storage. it requires a high reading speed. Generally, the reading speed from the physical hard disk cannot meet expectations. Therefore, I would like to try memory storage, however, I am hesitant to choose memcached or redis. please help me analyze whether my ideas are feasible and whether mem or redis should be used. My requirements are: 1. there are not many write operations, mainly reading operations; 2. there is no need to consider the memory size; 3. permanent storage, with a low failover rate. Thank you.

Reply to discussion (solution)

Memory storage image?
The image overhead is mainly the overhead of network transmission.
You should choose to store images in CDN instead of redis or memcache.

Memory storage image?
The image overhead is mainly the overhead of network transmission.
You should choose to store images in CDN instead of redis or memcache.
To explain, my application processes images. in a request, more than 20 images are processed, and a graph is generated at last. Therefore, the overhead of this image is not transmitted.

Redis
1. The maximum capacity of memcached is limited.
2. memcached does not automatically store the content on the hard disk and does not meet the requirements of permanent storage.