I still run "sync" before removing a USB drive. I'm sure it's entirely unnecessary now, but old habits die hard.

You definitely want to ensure buffers are flushed. Because very, very annoyingly it's not default behavior on Linux distros for removable devices to be mounted with write caching disabled. I don't even know of an easy option to make Linux do that. I think you'd need to write some custom udev rule

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aidenn0 2 days ago | parent [-]

> Because very, very annoyingly it's not default behavior on Linux distros for removable devices to be mounted with write caching disabled

About a decade ago, removable devices definitely were mounted with the "sync" option on some distros. It really tanked write performance though, so perhaps that's why they changed it. Certainly Plasma (and probably most DEs; I only use plasma) will tell you when the device is fully unmounted when you use the udisks integration.

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ziml77 2 days ago | parent [-]

The problem is that the write buffer turns copy progress into a complete lie. The last time I put a large file on a removable drive from Linux, the copy finished suspiciously fast. But I thought that surely Linux wouldn't be using a write buffer when Windows hasn't used that on removable devices for 20 years, so I went on my way and shut down the computer... which led to me just sitting at a gray screen. I had to just wait there with no indication of progress or even that it was doing anything at all.

If I wasn't aware of what was happening here I likely would have just force shut down the computer after a minute of waiting. And I suspect if I had done that and checked the drive it would have appeared like the file was there, while actually missing part of the data.

	▲	aidenn0 2 days ago \| parent [-]
		I did some digging and found: 1. Arch uses the "flush" mount option by default when using udisks (which is how removable devices are mounted interactively from a DE). 2. Manjaro has a package called "udev-usb-sync" that matches USB devices in udev and limits the write-buffer size. However, it appears to (by default, you can instead specify a constant value) calculate the buffer size based on the USB transfer speed, and given the fact that I have some USB 3.1 devices that cannot maintain 1MB/s of throughput while others that can maintain over 200MB/s of throughput and both report the same transfer speed to Linux, I don't know how effective it is.