|OS/400 Release:||5.4.5; 6.1; 6.1.1; 7.1; V5R4M0; V5R4M5; V6R1M0; V6R1M1; V7R1M0|
|Product:||OS/400 BASE (5722SS100)|
FTP Performance Considerations
This document discusses FTP performance/throughput (or any other single-threaded job) when using gigabit (or greater) Ethernet (non-WAN communication).
|1.||Network transfer rates are measured in bits, storage is measured in bytes. As a result, when comparing file transfer rates where you are transferring a 1 GB file, you need to remember that this is actually an approximate 8gBIT file on the wire. 1gps is approximately 135mBYTES/s.|
|2.||Gigabit Ethernet was designed for aggregate throughput that was much greater than that of 100mbs networks, meaning you could now have eight connections sending 100mbs versus eight connections sending 10mbs. Or, you could more likely have hundreds sending a few mbs versus those same hundreds sending less than a kbs.|
|3.||System resources have a much greater impact on single threaded bulk data transfers (which FTP is) than local, healthy LAN segments. CPU, DASD arms, main memory, pool sizes, and so on have a much greater bearing on this than the network link will have. When disk reads take approximately 10ms and writes take approximately 2 or 3ms, there will be time spent simply fetching and writing the data. Adding things like SAN storage or real time synchronous replication will make this process slower.|
|4.||Different file systems on the iSeries can greatly affect FTP transfer rates (assuming the resources are available for faster rates). From slowest to fastest, you have the following:|
o qsys.lib file in ascii mode
o qsys.lib file in bin mode
o root file system file (STMF) in ASCII
o root file system in bin
This is documented in APAR SE08885. Development has been working on making this faster; however, the issues are at the file system design layer and not at FTP itself, so this is not a trivial change. It will require a complete overhaul of the os400 file system handling code.
|5.||Any transfer rate approaching 150mbs - 200mbs is great. FTP must compete with all other tasks that are at the same priority for resources. System tasks (gigabit Ethernet send/receive tasks, for instance) run at a much higher priority so when these tasks have work to do, they get first chance at the system resources. If there are any left over in that cycle, then other lower tasks get their turn. If this system is in full production, these numbers are very good. If it is in preproduction or a test system, the expected transfer rates will most likely not be nearly this high once its moved to a production environment simply due to resource contention.|
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