Description of problem: Now that EDD has been re-enabled, there are two new command line options available which may be necessary for customers to use, in the event their system BIOS misbehaves. edd=skipmbr disables all BIOS calls which read data from the disks, but leaves enabled calls which probe the disk controller for information. This is useful when a system BIOS reports more disks attached than are actually present, which usually results in a 15-30 second delay during kernel startup. edd=off disables all BIOS calls related to EDD. As Alan Cox suggested, these need to be documented somehow in the RHEL4 docs, perhaps in the RELEASE-NOTES file or the installation docs. Please wordsmith as you feel necessary.
The following is a draft of what will appear in the release notes. Please let me know if there are changes needed. I am assuming that this feature appears only on the x86/AMD64/EM64T platform kernels. ------ The kernel shipped with Red Hat Enterprise Linux 4 now includes support for Enhanced Disk Device (EDD) polling, which queries for bootable disk device information directly from the disk controller BIOS and stores it as an entry in the /proc filesystem. Two significant kernel command-line options related to EDD have also been added: - edd=skipmbr -- disables BIOS calls that read disk data while stil enabling calls that request information from the disk controller. This option can be used when the system BIOS reports more disks than are actually present in the system, causing a 15-30 second delay in loading the kernel. - edd=off -- disables all EDD-releated calls to disk controller BIOS.
Yes, only x86_64 and x86 kernels. s/proc/sys, typos fixed below, otherwise looks good to me. The kernel shipped with Red Hat Enterprise Linux 4 now includes support for Enhanced Disk Device (EDD) polling, which queries for bootable disk device information directly from the disk controller BIOS and stores it as an entry in the /sys filesystem. Two significant kernel command-line options related to EDD have also been added: - edd=skipmbr -- disables BIOS calls that read disk data while still enabling calls that request information from the disk controller. This option can be used when the system BIOS reports more disks than are actually present in the system, causing a 15-30 second delay in loading the kernel. - edd=off -- disables all EDD-releated calls to disk controller BIOS.
Great. Thank you for the correction. I've added this to the Release Notes and am closing this bug.
Confirmed, added to the RC1 Release Notes. Removing this from RHEL4ZILLA.