If you are having problems with slow transfer speeds, try fine tuning Deva xFTP Try the following:
Mode Z compression compresses files as they are transferred. Reducing the file size reduces the necessary bandwidth and improves transfer times. If this option is turned on Deva xFTP will take advantage of any server that supports Mode Z.
Setting these buffers allow you to fine tune transfers over high latency or lossy connections like those over satellite links or with legacy CDMA wireless connections. It is unlikely you will ever need to adjust this setting, but if you have problems with successful transfers and suspect the latency or quality of the connection is at fault, try tweaking these buffers.
Receive buffer holds data until Deva xFTP is ready to read it; the send buffer holds data until it can be sent to the server. Typically, both send and receive buffers should be set to the same size. The default is set at 65536 bytes, the normal maximum window size of TCP.
You can measure the latency and estimate the available bandwidth with network monitoring tools. There is some guesswork involved, as most tools are not entirely accurate, but they can guide you to finding a sweet spot where transmissions are successful. If you have a lossy connection, try lowering the buffer size. If you have high latency, a higher buffer size might help.
Normally, the optimal buffer size is your bandwidth times the latency of the link. So,
bandwidth (in bits) * latency (round trip time in seconds) = socket buffer size (in bits)
Convert bits to bytes (bits/8=bytes) for the buffer size.
So, if your bandwidth is 1,536,000 bps and you have a latency of 200ms (.2 seconds), your socket buffers should be set to 38400:
1536000*.2=307200 bits
307200/8=38,400 bytes
You can also try halving or doubling the buffer size. For example, if the buffer is set to 65536 (64kb), try 32768 (32kb).
When this feature is on, Deva xFTP adds a time stamp next to each log event. This option does consume system resources, and if performance is critical, you can turn this off. For more information, see Record/Display time stamps in Log file settings
Check to see if the global bandwidth limit is limiting your throughput. This setting in GlobalOptions throttles the bandwidth of all sessions on Deva xFTP. See Global bandwidth limits in Transfer Settings.