Bypass storage class memory read cache based on a queue depth threshold

An article comprising at least one non-transitory machine-readable storage medium comprising instructions executable by at least one processing resource of a storage system to:

• determine a total amount of data read from and written to a storage class memory (SCM) read cache in a given time period;
• adjust at least one of a read and a write queue depth threshold for the SCM read cache in response to a determination that a data rate threshold for the SCM read cache is exceeded, based on the determined amount of data;
• in response to an input/output (IO) request for the SCM read cache:
• when processing the IO request includes writing to the SCM read cache and a current number of write IOs outstanding for the SCM read cache is greater than the write queue depth threshold, drop the IO request;
• and
• when the IO request is a read request for requested data and a current number of read IOs outstanding for the SCM read cache is greater than the read queue depth threshold, bypass the SCM read cache and read the requested data from backend storage of the storage system or from a remote computing device into the main cache of the storage system.

A storage system comprising:

• at least one processing resource;
• a main cache;
• a storage class memory (SCM) read cache;
• backend storage;
• and
• at least one non-transitory machine-readable storage medium comprising instructions executable by the at least one processing resource to:
• perform a background process comprising:
• determining an amount of data transferred to and from the SCM read cache in a given time period;
• and
• adjusting at least one of a read and a write queue depth threshold for the SCM read cache in response to a determination that, based on the determined amount of data, a data rate threshold for the SCM read cache is exceeded;
• and
• perform an input/output (IO) process comprising:
• in response to an IO request for the SCM read cache:
• when the IO request is a request to destage data to the SCM read cache and a write queue depth of the SCM read cache is greater than the write queue depth threshold, drop the IO request without writing the data to the SCM read cache;
• and
• when the IO request is a read request for requested data and a read queue depth of the SCM read cache is greater than the read queue depth threshold, bypass the SCM read cache and read the requested data from the backend storage or from a remote computing device into the main cache.