[JSch-users] SFTP slow file transfer speed with Titan FTP

[Thomas K. <tho...@ou...>]

Hi!


We're using Camel<http://camel.apache.org/> to read files from a SFTP server. Camel is using JSch internally which used to work quite good for us. I recently had to upgrade JSch in our product from 0.1.38 to 0.1.53. Although the upgrade works perfectly with the majority of our customers I am currently faced with a weird issue with Titan FTP (SSH-2.0-srtSSHServer_11.00). The transfer speed by using Channel#get(String) is awfully slow (~ 10 KB/s). I tried several JSch versions and observed that the issue had been introduced in the transition of 0.1.47 to 0.1.48 whose changelog states:


    - change: the file transfer speed with ChannelSftp#get(String src) has been

          improved; sending multiple requests at any one time.
    - change: by the default, at most, 16 requests will be sent at any one time
          in ChannelSftp.


Before this change the download rate was at least at several 100 KB/s. So, I'm particularly interested in "sending multiple requests at any one time" in ChannelSftp. What does it mean and how can this actually result in a download slow down?

Current work around is to make use of ChannelSftp#get(String, OutputStream) which is still satisfactorily fast. For testing purposes I set the number of bulk requests to 1 which resulted in a known good performance.

I already tried to use ChannelSftp#setBulkRequests(int) but with no luck. Current work around is to make use of ChannelSftp#get(String, OutputStream) which is still satisfactorily fast.

Any hints are appreciated!

Regards,

-- Thomas