Security and Technology Ramblings…

It’s bizarre how a great operating system like OSX would have such a massive, but simple to fix issue.

I noticed recently when trying to move several large files across a samba/cifs share that it was painfully slow. In some cases, large files were about as slow as I would expect to see going across a dial up modem connection.

To fix this issue you will need to create a file under /etc/ called sysctl.conf. Then add a single line to it like this: net.inet.tcp.delayed_ack=0

To do this in one easy step, you can just do this…

1. Open a terminal window.
2. Type in: sudo echo “net.inet.tcp.delayed_ack=0” > /etc/sysctl.conf

The difference is amazing.

Hey, Apple! Make this a default change in your next release! Or maybe a bug fix?

One Response to Slow CIFS / Samaba File Sharing under OSX

  • What do you suspect the issue is? I have noticed intermittent slowness on network transfers or even mounted drives. Then, suddenly, the issue clears itself up.

    My limited understanding of the code you provided indicates some issue with the way the two machines across the share are talking “about” the transfer of the packets. Is this right?

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