On Fri, 2006-03-03 at 16:58 +0100, Stefan Richter wrote: > James Bottomley wrote: > > Assuming the cages are all powered up, which is beyond > > the driver control, then serialising the scan will allow one to > > specify /dev/sda1 deterministically for root. > > Does SAS provide a persistent globally unique property of a device, or > has SAS to rely on bus topology to uniqely identify devices? Yes ... naturally; all modern SCSI devices provide a variety of ways of identifying them. In the fullness of time, I expect udev and initramfs to support all of these, allowing the user free range of specifications. I also expect the boot system to provide a timeout (or wait forever) parameter for delaying before these become visible. However, none of these problems are kernel issues. The problem, currently, isn't really waiting for the root device (which is well known and solved) it's that with random ordering you're forcing the udev method ... which may not be a bad thing, but not one I'm necessarily willing to push at the moment. So the intent is to add enough determinism for most simple SAS boot systems to function on the current /dev/sd method. It can be altered later. James - : 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
