On Tue, Jul 08, 2014 at 12:15:54AM +0800, loody wrote: > so sg_read will not hammer on the page cache like dd without "iflags=direct" > > thanks for your kind help, The sg_read program (and other programs in sg3_utils) sends a command directly to the device using an SG_IO ioctl. This bypasses all the caching layers in the kernel and always results in IO to the device (if it succeeds). Regards, Bryn. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html