On Tue, Mar 29, 2005 at 11:32:16PM -0500, John Richard Moser wrote: > Does crossing a > track boundary incur anything expensive?
AFAIK, yes. It's going to involve some kind of seeking (even a head switch needs microjogging on modern drives), and it will certainly add latency (although I don't remember how much, off the top of my head). However, trying to control this from the kernel may be vastly harder than you're expecting (assuming a modern hard drive). You may want to look at these pages for more info: http://www.storagereview.com/guide2000/ref/hdd/geom/tracksZBR.html http://www.storagereview.com/guide2000/ref/hdd/geom/geomLogical.html Also look at the last paragraph on this page -- not the paragraph with the "Stop" sign, but the one after it: http://www.storagereview.com/guide2000/ref/hdd/geom/formatDefect.html I think this could in fact be done, but it would be a lot of effort, and the kernel would need knowledge on a per-drive-model basis (or at least it would need a way to obtain such knowledge from user space, and the per-model knowledge would need to be stored there somehow). For all I know, vendor-specific commands might also be needed in order to find out which blocks are remapped, in order to use that knowledge to avoid changing tracks spuriously. (And one other note: Since your device almost certainly has many tracks with well over 256 sectors in reality, your device is actually incapable of reading or writing a single track with a single ATA command unless it supports LBA48.) -Barry K. Nathan <[EMAIL PROTECTED]> - 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/