John,
What sort of data rate do you see just copying this file to another using
TSO COPY or IEBGENER, for example? That would give you an idea of what your
disk subsystem was capable of. Considering the TCPIP and FTP protocol
overhead, 40 MB/sec doesn't sound too bad.
I have also had customers come to me with issues about slow FTP performance
which, on inspection, was caused by use of inappropriate blocksizes on the
z/OS output file. Something they wouldn't normally have a problem with if
specifying DCB parms in a JCL deck, but don't think about when they are
FTP'ing.
Also note that hipersocket performance is affected by CPU utilization
utilization. I don't know what the exact relationship is, but I have
measured that is does occur.
Finally, I should explain the 200 MB/sec results I mentioned in my previous
post. They were produced during testing to see what sort of throughput
hipersockets could actually deliver using FTP (in order to correct
misinformation floating around the shop that "hipersockets is slower than
the regular network"). I was FTPing between two virtual Linux servers
running on the same single-IFL z9-109. CPU utilization was <10% at the
time. In order to remove DASD performance as a variable, LINUXA had a 256MB
file, in cache. LINUXB did an FTP "get" from LINUXA, directing the output
into /dev/null. Elapsed time was on the order of 1.2 seconds. SCP of the
same file, on the other hand, only ran at about 8 MB/sec. Investigation
showed that each Linux virtual machine was running at >45% CPU - encrypting
the file on one end and decrypting it on the other (in software, since we
don't have a hardware crypto facility). Dunno why one would need to encrypt
data over a hipersocket link, but someone is bound to do so. So heads up,
y'all, if they come to complain...
Mark Wheeler, 3M Company
"John S. Giltner,
Jr."
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On a z990-303 with a single IFL and 3 CP's using 56K MTU's. No matter
what I did I could only get 40MB ps using FTP. However, I could get
somewhere between 3-5 FTP streams running concurrently with 40MB ps
each, total of 120-200 MB ps
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