SSH Reference Manual

SFTP clients that retrieve the file attributes for each file matching the specified pattern again from the SFTP server. This
is causing unnecessary overhead. If the delay is of unacceptable length, the following workarounds may help:
• Reduce the number of files in one directory/subvolume on NonStop
• Set USER attribute SFTP-GUARDIAN-FILESET if information of files in a Guardian subvolume is listed. In
this way the pattern matching is done on the server and the data being sent to the client can be greatly reduced.
Different patterns can be defined by using different ssh user records with the same SYSTEM-USER.
Performance When Running as SSH Client
The above measurements have been repeated with the SFTP client now running on the NonStop system. The following
table shows the result of the measurement:
Partner
system
Direction of
transfer
Cipher
Suite/MAC
algorithm
Time
elapsed [s]
CPU time
used [s]
Through-put
[KB/s]
CPU ms/MB
transfer
CPU usage
Linux,
OpenSSH
NonStop to
Partner
system
AES-
128/MD5
54 26,2 904 549 48 %
Linux,
OpenSSH
Partner
system to
NonStop
AES-
128/MD5
238 28,0 205 586 12 %
Summary
There is no answer to the seemingly simple question: "How much CPU cycles will 128 bit encryption consume on my
system?" To understand why, consider asking an automobile expert the question, "How much fuel will I need for my
vacation?" (Without giving away more information.) Regardless of how much the expert knows about cars and engines,
he will not be able to give an answer unless you tell him such information as…
• The maker of the car.
• Where you want to go.
• Your driving habits.
Using the data provided in this chapter should allow you to get an estimate of the CPU resources that should be utilized
by SSH2 within your specific environment.
HP NonStop SSH Reference Manual Performance Considerations • 329