On Fri, 28 Jan 2005 16:15:40 -0600, Doug Maxey <[EMAIL PROTECTED]> wrote: > > On Fri, 28 Jan 2005 22:49:08 +0100, Bartlomiej Zolnierkiewicz wrote: > >On Fri, 28 Jan 2005 15:43:52 -0600, Doug Maxey <[EMAIL PROTECTED]> wrote: > >> > >> On Fri, 28 Jan 2005 22:35:17 +0100, Bartlomiej Zolnierkiewicz wrote: > >> >On Fri, 28 Jan 2005 15:06:22 -0600, Doug Maxey <[EMAIL PROTECTED]> wrote: > >> >> > >> >> On Fri, 28 Jan 2005 20:11:37 +0100, Bartlomiej Zolnierkiewicz wrote: > >> >> >On Fri, 28 Jan 2005 12:16:01 -0600, Doug Maxey <[EMAIL PROTECTED]> > >> >> >wrote: > >> >> > > >> >> >We have too many config options already. > >> >> > > >> >> >Behavior should be simple: > >> >> >* no cache flushes - wcache off by default > >> >> >* cache flushes - wcache on by default > >> >> >* inform user about the wcache status > >> >> >* allow changing of wcache by user > >> >> > >> >> My interpretation of what you are saying here is the selection of > >> >> "cache flush" drives the setting of wcache. Are you saying that > >> >> "barrier=off" on the boot line the currently (only and will remain) > >> >> supported method controlling flushes? > >> > > >> >No, I am saying that cache flush is a property of disk not fs. > >> >On the contrary barrier is a property of filesystem. > >> > >> Ok. We are talking apples and oranges here. The disk DOES have FLUSH > >> CACHE, > >> which is the main reason these drives work in the later kernels. You can > >> switch wcache back and forth, provided that the correct flushing is done. > >> > >> Write cache, on the otherhand, which is disabled on the drive by default, > >> is not honored. > > > >What is the practical reason to honor it? > > The datacenters/server folks that would be using these drives would > expect them to remain as set. I have to check, but unless something > has changed very recently in the kernel, setting with hdparm does not > "stick" in the sense that the command succeeds to the disk, but no change > is made to the barrier.
It is not a problem for IDE driver (flushes become no-ops) and this way you can later enable wcache and still use barries. > here is the current scenario with a drive that can work with wcache off. > - idedisk_setup() forces enabled wcache. > - enabled wcache uses FLUSH. > - hdparm -W0 disables cache without matching change to barriers. > > - Setting "barrier=off" has the undesired side effect of not flushing > with wcache enabled on the drive. Some people with certain servers are > _ssooo_ picky. :) This is fs layer problem. - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
