hdfread, NFS, and I/O Performance

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millercommamatt 2014-7-18

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https://ww2.mathworks.cn/matlabcentral/answers/142465-hdfread-nfs-and-i-o-performance

I'm encountering a vexing performance issue.

I have a script that uses the hdfread command to get variables from HDF files stored on a remote directory mounted in Windows via NFS. I wrote a benchmarking script that's telling me that when I try to read data from the network mounted directory, it's taking about 196 seconds per file. If I copy those file to a local directory and point the hdfread command at that directory, it's taking 3 seconds per file.

Here's were things get interesting. Copying and pasting the files in Windows sees them all copied in only a second or two per file. I used the copyfile command to copy the files from the remote directory to a local folder. The per file copy time is 2 seconds per file. It would seem that network I/O doesn't explain the extreme slowness.

Is there something about the hdfread command or its subfunctions that can explain this behavior? Is there some quirk about network file systems at play that I'm not aware of?