Question : Slow FTP transfer between Mainframe with OSA card and Windows 2008 Server

We are trying to increase the speed of FTP transfters of a 1GB file from our ZOS Mainframe to a Windows 2008 Server.  Currently we transfer a 1GB file, over a 1Gbps link, at speeds close to 28500Kbytes/sec.  This takes close to 40 seconds to complete.  I have tried doing this ftp between the mainframe and a windows 2003 server and played with the TCP windows sizing and nothing I tweak seems to help.  On the 2008 server I've tweaked the autotuning level by disabling it and this doesn't help.  I currently have the mainframe directly connected to the windows server with a cross over cable to eliminate any network slowness.  I get the same kind of speeds when I transfer this file over the network also.  I have directly connected two windows servers and done the ftp with 100492Kbytes/sec for the same 1GB file and it's done in about 10 seconds.  We have also played with the window size on the mainframe at 64K, 128K and 256K and these settings don't seem to make any drastic improvements.  Has anyone else out their worked with transfering files via FTP from a mainframe to a Windows server and got good speed results?

Answer : Slow FTP transfer between Mainframe with OSA card and Windows 2008 Server

Just checked, we do have OSA Express 2.  From my testing and experience when using 1500 byte frames the best you can get is 40MB/sec.

Did you mean "Jumbo Packed" or "Jumbo Packets?"

Right no I have no access to an enviroment where I can test using Jumbo frames.  I do seem to remember getting in the 70-80MB/sec range doing early ftp testing to/from a distributed box, but I was told that was the limitation of the I/O rate on the distributed boxes disk system.

IIRC the biggest difference between the OSA Express and the "2" card is the ability to do TCP packet segmentation offload, but this was broken badly and the last I checked IBM's recommendation was to leave it disabled.  With segmentation enabled, it could disable the OSA adapter and if you don't have a second one, you loose access to your system.   In some instances it was an IPL to get it back.  We had it happen to us, but luckily we had a second OSA for backup and recovered the OSA without an IPL.  There may have been a slight performance improvement between the Expresss and the "2".