ArcGIS Server 10.7.1: What is the best practice for storing cached map service?
I couldn’t figure out regarding the best practice for storing cached map service:
Which one is better: NAS, SAN, local file storage or other?
In case of slow performance, what could be the reason: CPU, RAM, Network, number of instances, or something else?
For cache storage, a directory local to the ArcGIS Server machine will usually be the fastest/best performing as long as it has enough disk space to hold the cache, as it does not need to access the cache tiles over the network. Placing identical file geodatabases on each server machine (if you are using a multi-machine deployment) usually performs the best for caching workflows.
If you are experiencing slow performance, it could be network or system resources as you stated above, but it could also be caused by an antivirus or threat scanning software. Make sure the cache directory folder is added as an exception to your antivirus.
Hope this helps.
But what if the cached map services are stored on SAN with fiber connection (40Gbps). Is this equivalent to local file storage?
This is something that should really be tested within your own environment to compare the performance, as it's difficult to say for certain. Although a 40gpbs connection should be expected to perform quite fast, the behavior could be vastly different when the network is under heavy load, and without proper load testing it is impossible to say if it would be equivalent to local file storage.