FTP : overwriting a file
Hello to the group !
Hopefully someone can shed some light on this for me .......
Scenario :
Linux box used as FTP client connecting to Windows 2000 FTP Server. Binary mode transfer from Windows to Linux using GET command. Filesize of remote file is ~ 42GB 1st GET is successful and transfer via data connection is immediate. 2nd GET of same file takes longer to start the transfer.
The question :
Why does the 2nd GET of the same file take longer to begin transferring ?
What I have found so far :
To put it simply, if the info isn't available in a syscall, you can't get it except from the logs of the bootup or proc (where what the kernel thinks...
The length of time before the 2nd GET transfer begins seems to vary depending on the distro of Linux used. Debian Sarge, SuSE ES 9, and SuSE 10 Pro all seems to behave in the same way ( ie ~60 seconds pbuttes before the transfer actually begins). However, RedHat 9 does not seem to exhibit the problem. I think I have narrowed the issue down to the time it takes for a file to actually reach a 0 byte size level on overwrite....
When you have a 42GB file sitting in a directory and you try to overwrite that file with an FTP transfer (ie GET of the same filename) there is a delay of about 60 seconds before the data connection actually starts to transfer. This delay corresponds with the amount of time it takes for the filesystem to report a 0 byte file size for the file being overwritten. As soon as this file reaches 0 bytes then the data connection begins the transfer.
So, why is it that I do not see this problem with Red Hat 9 (kernel 2.4) but it is apparent with SuSE ES 9 (kernel 2.6), SuSE 10 Pro (kernel 2.6) and Debian Sarge (kernel 2.4) ?
Can anyone shed any light onthis for me ?
Please ask if you need more info!
Many thanks
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