Query regarding "write" system call.

Hi all,
I am a newbie to Freebsd OS. I had a query regarding performing writes onto
a disk.

Generally when we want to write some data we first copy the data from the
processes user space to the kernel buffer and hand this buffer to the device
driver who then goes and initiated a write to the h/w.

Now my question here is that the kernel buffers are very limited in size ,
what happens if i have a really huge chunk of data to be written, won't the
above mechanism of copying from userland to kernel buffer be slow ?

thanks,
Abhiman
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