Hello,

I'd like to find out how to turn of USB buffer in Linux, but I find no answer either on google or here. It's not an option for USB HDs that they get actualized when I unmount them.

Thanks,
A.

Maybe you are thinking of using the "sync" mount option, so that all IO is done synchronously.
This may degrade performance. Also, don't use this option for flash drives. It might shorten their lifespan.

You can stick with async, but type sync before you unmount the drive.

Thank you for you quick replies.

I'd be sad, if 'sync' was the only option for a "bufferless" USB disk. Sync makes the device way too slow. I'm thinking of a Windows way of handling the problem.
There I could choose not to buffer the data, but flush it immediately.

How would unmounting with sync help Linux to flush the data immediately without storing it in memory?

I intend to buy a USB/Firewire external HDD, and I really don't want my linux to keep files in the memory if I copy something. Also 'sync' is out of the question, because its slow.

I don't know if firewire drivers have this "optionless state" since I have no device to test it with.

Linux buffers and cache data, so you can not get around these issues especially for SCSI devices. Again before you unmount type sync to force dumping the data to the storage medium.

Another way is to use floppy utilities in Linux. It should not buffer or cache the data.

I normally use the following to mount and unmount USB storage devices.
mount -t vfat -o rw,umask=000,async,quiet /dev/sda1 /mnt/usbdisk

sync && umount /mnt/usbdisk && echo "It is now safe to remove the USB drive (/dev/sda)!!!"

I do not include the echo command in my commands, but for most people they feel a lot happier when see human readable text.

Though, I do not know why you are making a lot of fuss over this issue.

You're gonna tell me if I'm wrong or paranoid about that, but

Having a huge external HDD that is not up-to-date, and then
- having system failure, because once in a millenia it happens, could disappear a whole movie buffered in memory. Or worse, only parts of it, which I might never even realize.
- having shut down quickly, but then it starts flushing the data.
What would it do with an external DVD-RW device?

Doesn't sound very promising. You might say that 1-2 GBs should be flushed to disk very quickly. And indeed, it is rather a mental thing.

But you say it's OK, so I go for it. Thank you for your answers!