I mounted a ftpserver into my local OS:
curlftpfs user:pass@ftp.server.com /var/test/
I noticed using pydf that there is maximal size of this volume at about 7.5GB:
Filesystem Size Used Avail Use% Mounted on
curlftpfs#ftp://user:pass@ftp.server.com 7629G 0 7629G 0.0 [.........] /var/test
Then I tried to fill the disk space using dd with an 8GB file but this failed also at the given size:
dd if=/dev/zero of=upload_test bs=8000000000 count=1
dd: memory exhausted by input buffer of size 8000000000 bytes (7.5 GiB)
The FTP user has unlimited traffic and disk space at remote server. So my question is: Why is there a limit at 7.5GB and how can I skip it?
Looking at the source code of curlftpfs 0.9.2, which is the last released version, this 7629G seems to be the hardcoded default.
In other words, the curlftpfs doesn't check the actual size of the remote filesystem and uses some predefined static value instead. Moreover the actual check can't be implemented because ftp protocol doesn't provide information about free space.
This means that failure of your file transfer on 7.5 GB is not caused by reported free space, as there is an order of magnitude difference between the two.
Function ftpfs_statfs implementing statfs FUSE operation defines number of free blocks as follows:
buf->f_blocks = 999999999 * 2;
And the size of filesystem block as:
buf->f_bsize = ftpfs.blksize;
Which is defined elsewhere as:
ftpfs.blksize = 4096;
So putting this all together gives me 999999999 * 2 * 4096 / 2^30 GB ~= 7629.3945236206055 GB, which matches the number in your pydf output: 7629G.