Write Bytes Cache/sec is the rate at which applications on your computer are writing to the file system cache by using the ...

Write Bytes Cache/sec is the rate at which applications on your computer are writing to the file system cache by using the Redirector.  The data might not leave your computer immediately; it can be retained in the cache for further modification before being written to the network.  This saves network traffic.  Each write of a byte into the cache is counted here.