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Using load/save on a network drive at full speed.

Asked by Andrew Metcalf on 9 Sep 2016
Latest activity Answered by Douglas
on 3 Apr 2017
I have a network drive on which I store my data and .mat files. Using Windows Explorer, I can move and copy files at nearly the full 1 Gbps connection, typically getting about 950 Mbps throughput. In Matlab R2016a, when I navigate to this same folder and double-click a .mat file to load it, essentially running a "load('filename.mat')" command, I can see with Task Manager that I am only getting about 130 Mbps throughput. Does anybody have any ideas for how to get Matlab to utilize the full speed of my connection?
Note that for some files, I can actually get the full speed - I'm trying to figure out what might be different about these files (i.e. compressed v uncompressed, but I can't find any consistent correlations yet). Another thought I had was that maybe Windows is limiting network access for the Matlab process, but when I look at advanced network stats with a program called NetBalancer, the file loading from the network drive is actually routed through the "System" process and is not directly accessed by Matlab.
Thanks for any help and ideas.

  2 Comments

What about a 2-step process ... copy file to local drive (e.g., C:) and then load? Is that combo faster overall?
Ok, I've done some more investigation - including this suggestion of copying to local drive then loading. Overall, there is not much increase in speed, if any at all (I didn't do a rigorous tic-toc, but am going by observation).
My current thinking is that the cause for slowness is compression of the v7.3 .mat file format. Apparently, uncompression is a single-core process. Because my network access is fast enough to keep up with the CPU, the increased speed of a local SSD makes no difference in load time. If I happen to load a v6 .mat file across the network, I can see that access to the file is 900+ Mbps.
So, any ideas from the community on how to deal with this? What are some best practices that some of you have come up with?
I have already written my own "save" function that will attempt to save my variables as a v6, then v7, then v7.3 .mat file so that it defaults to uncompressed data if it can. Besides that, I would love to be able to deal with the v7.3 files in a much better way.
The best idea I can think of right now would be to determine which of my variables are too big for an uncompressed file and then save them separately with the hopes that I don't need to access them very much in the future. Then (hopefully) the parts that I do continually load for further analysis can be in an uncompressed format. The problem: how do I properly keep track of the increase in number of .mat files per experiment? I would love to hear suggestions about this.
Also, can Mathworks work on multi-threading the 'load' command?

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1 Answer

Answer by Douglas
on 3 Apr 2017

Hi everybody. I'm having the same problem. While saving .mat (~2.4 GB) files using -v7.3 to a shared folder (using NFS to share the folder between machines) it achieves only 0.5 MB/s in a GB network. Does anybody know if the Matlab team has released some workaround?

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