Hello,
z/OS 2.5, Co:Z COZBATCH version 8.1.1
I have made some observations about the use of various ciphers and their effect on transmission speed / performance. According to the IBM OpenSSH documentation, the aes256-ctr ciphers are eligible for CPACF, whereas the aes256-GCM@openssh.com are not. The aes256-gcm seem to be faster with throughput, but come with an additional general CPU penalty since they cannot offload work to the CPACF processors. The aes256-ctr is slower for throughput, but doesn't incur the general CPU penalty because of CPACF offload.
As far as tuning is concerned, are there any things that can be done to sftp to improve the slower throughput while using the aes256-ctr cipher ? I know there is "-B buffersize" parm that can be used, but seems this is limited to certain maximum values (128K) , exceeding this causes the "Outbound message too long" in the logs.
Mark