On Tue, 25 Mar 2008 13:45:35 -0400 Greg Freemyer wrote: > On Tue, Mar 25, 2008 at 11:17 AM, James Bottomley > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, 2008-03-25 at 00:02 -0400, Mark Lord wrote: > > > (resending .. forgot to copy the lists originally) > > > > > > We have a problem coming down the pipeline. > > > > > > Practically all utilities that care about it, > > > use ioctl(fd, HDIO_GETGEO) to determine the starting > > > sector offset of a hard disk partition. > > > > > > SCSI, libata, IDE, USB, Firewire.. you name it. > > > > > > The return value uses "unsigned long", > > > which on a 32-bit system limits drive offsets to 2TB. > > > > > > There will be single drives exceeding this limit within > > > the next 12 months or less, and we already have RAID arrays > > > that exceed 2TB. > > > > > > So.. what's the replacement for HDIO_GETGEO on 32-bits ? > > > > > > One candidate might seem to be the existing /sys/block/dev/partition/start > > > which I expect is already 64-bit friendly. > > > > > > But this requires about 150 lines of somewhat complex C code to access, > > > using only the dev_t (from stat(2) on a file) as a starting point, > > > or less if one relies upon the udev device name matching the sysfs device name. > > > > > > Is it time now for HDIO_GETGEO64 to make an appearance? > > > Similar to how the existing BLKGETSIZE64 is supplanting BLKGETSIZE ? > > > > Perhaps I've missed something, but surely geometry doesn't make sense on > > a >2TB drive does it? The only reason we use it on modern disks (which > > usually make it up specially for us) is that the DOS partition scheme > > requires it. Once we're over 2TB, isn't it impossible to use DOS > > partitions (well, OK, unless you increase the sector size, but that's > > only delaying the inevitable), so we can just go with a proper disk > > labelling scheme and use BLKGETSIZE64 all the time. > > > > I believe GUID Partition Tables (GPTs) are the answer. > > I believe one of the features of GPT is the elimination of the 32-bit > sector restrictions. > > http://en.wikipedia.org/wiki/GUID_Partition_Table > > Windows VISTA 64-bit supports GPTs on data disks and new Mac OS based > systems have been using it on internal drives for a couple years at > least. > > GPTs are part of the Extensible Firmware Interface (EFI), so they > should be usable for PC bootable disks at some point. (Maybe now in > some cases?) > > I'm not sure what the Linux Kernel support is for GPTs. It's implemented. Not sure about how well used/tested it is. config EFI_PARTITION bool "EFI GUID Partition support" depends on PARTITION_ADVANCED select CRC32 help Say Y here if you would like to use hard disks under Linux which were partitioned using EFI GPT. --- ~Randy -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
