On Mon, 7 January 2008 13:25:09 +0100, Frantisek Rysanek wrote: > > let me start with a simple example. The following commands: > > cp /dev/zero /dev/hda > dd if=/dev/zero of=/dev/hda [bs=512] > > both have one common side-effect: apart from the disk being properly > overwritten with zeroes, the kernel seems to keep reading sectors > ahead of the current seek position of the sequential write.
Block devices are cached in the page cache. If you write less than a full page, any remainder has to be read from the device. If you retry the dd with bs=4096 (or whatever your architecture's page size happens to be), does this still occur? Jörn -- Chance favors only the prepared mind. -- Louis Pasteur -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
