Re: A weird disk behaviour

[Zhihui Zhang]

On Wed, 6 Mar 2002, Peter Edwards wrote:

> Zhihui Zhang wrote:
> 
> <snip>
> 
> > ... I also do not read anything during the partial block write,
> > and I think the disk controller should not do that either.
> 
> If you do a partial block write, surely at some point the block must be read
> in order to preserve that segment of data you are _not_ overwriting?

First off, I am not writing through any file system. I access the raw
device directly.  Secondly, the bytes written are always a multiple of 512
bytes. If one sector is the I/O unit of a disk controller, why should it
read anything to prevent overwritten?

-Zhihui 


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