I/O request type specific cache directories

A computer system, comprising:

• one or more processors, one or more computer-readable memories including a cache, and one or more computer-readable, tangible storage devices having program code embodied therewith, the program code executable by at least one processor to perform:
• receiving by a storage controller from a host, a first input/output (I/O) request of a first I/O request type and having a first I/O request type identification (ID) identifying the type of the first I/O request, wherein the first I/O request requests a first I/O operation directed to a first data unit;
• in response to receipt of the first I/O request, selecting a first I/O request type specific cache directory as a function of the first I/O request type ID wherein the first I/O request type specific cache directory indicates whether a particular data unit is stored in the cache and is limited to entries identifying data units cached in the cache for I/O requests of the first I/O request type;
• performing a first look-up for the first data unit in the selected first I/O request type specific cache directory to determine if the first data unit is cached in the cache;
• in response to the first look-up successfully locating a first entry of the first I/O request type specific cache directory identifying the first data unit as cached in the cache, performing the requested first I/O operation of the received first I/O request using the first data unit cached in the cache;
• and
• in response to the first data unit look-up failing to successfully locate an entry of the first I/O request type specific cache directory identifying the first data unit as cached in the cache, the first I/O request is failed instead of being performed.

A computer-implemented method, comprising:

• receiving by a storage controller from a host, a first input/output (I/O) request of a first I/O request type and having a first I/O request type identification (ID) identifying the type of the first I/O request, wherein the first I/O request requests a first I/O operation directed to a first data unit;
• in response to receipt of the first I/O request, selecting a first I/O request type specific cache directory as a function of the first I/O request type ID wherein the first I/O request type specific cache directory indicates whether a particular data unit is stored in the cache and is limited to entries identifying data units cached in the cache for I/O requests of the first I/O request type;
• performing a first look-up for the first data unit in the selected first I/O request type specific cache directory to determine if the first data unit is cached in the cache;
• in response to the first look-up successfully locating a first entry of the first I/O request type specific cache directory identifying the first data unit as cached in the cache, performing the requested first I/O operation of the received first I/O request using the first data unit cached in the cache;
• and
• in response to the first data unit look-up failing to successfully locate an entry of the first I/O request type specific cache directory identifying the first data unit as cached in the cache, the first I/O request is failed instead of being performed.