Cache prefetching in offloaded data transfer (odx)

Abstract

Cache prefetching in offloaded data transfer (ODX) processes. A populate token command is received to initiate a copy offload operation. Responsive to receiving the populate token command, a cache of a data storage system in a storage area network environment is instructed to prefetch data in accordance with the populate token command and complete an offloaded read request. Responsive to determining that a write using token command is not received within a specified time duration, the prefetched data stored in the cache is evicted.

What is claimed is: 
     
         1 . A method comprising:
 issuing, by one or more computer processors, a small computer system interface command from a client application to a copy manager that manages a data storage system to transmit a first populate token command;   receiving, by the one or more computer processors, the first populate token command to initiate a first copy offload operation;   responsive to receiving the first populate token command, prefetching, by the one or more computer processors, a first set of data in accordance with the first populate token command in sequentially with completing a first copy offloaded read request;   transferring, by the one or more computer processors, the first set data from one logical unit to another logical unit in an offloaded data transfer process using the copy manager;   responsive to determining that a first write using the first token command is not received within a specified time duration, adding, by the one or more processors, the first set of prefetched data stored in cache to a list of cache pages that can be evicted, wherein the first set of prefetched data stored is at a top of the list of cache pages that can be evicted;   evicting, by the one or more computer processors, the first set of prefetched data stored in cache;   receiving, by the one or more computer processors, a second populate token command to initiate a second copy offload operation;   responsive to receiving the second populate token command, prefetching, by the one or more computer processors, a second set of data in accordance with the second populate token command in parallel with completing a second copy offloaded read request;   responsive to determining that a second write using the second token command is received within the specified time duration, completing, by the one or more computer processors, the second write using the second token command; and   responsive to completing the second write using the second token command, evicting, by the one or more computer processors, the second set of data stored in the cache, wherein the second set of data stored in the cache is not added to the list of cached pages.