M5 Onboard Intel RAID and SAS Cards: Archived Disk-Ordering Workaround

The source reports varying OS disk enumeration when onboard Intel RAID and an external LSI9400/SAS adapter coexist. It attempts to control loading order with AHCI and a custom udev rule. Such enumeration is not a stable storage identity: verify the real devices and use supported persistent identifiers for mounts/operations rather than assuming sdX always denotes the same drive.

Driver and file prerequisites

The source references 18-scsi-sd-sequence.rules, but does not include its complete content or a usable download. Its pictures show only a fragment using DRIVERS=="megaraid_sas" and a wait for /dev/sda. Do not reconstruct the missing rule from that fragment. The HTTP URLs containing xxx are placeholders, with inconsistent sd-sequence/sdsequence filenames.

The source names megaraid_sas for the applicable LSI RAID branch, mpt3sas for its SAS/HBA branch, and misspells a PMC/Adaptec driver as “accraid.” The common driver spelling is aacraid, but select the driver actually used by the controller; newer PMC/Microchip controllers can use other drivers. The rule cannot be selected safely from the vendor name alone.

A. Source workaround after OS installation

For the source’s RHEL/CentOS6 UEFI example, edit the active /boot/efi/EFI/redhat/grub.cfg kernel line to add rdloaddriver=ahci, then install the vendor-verified rule in /etc/udev/rules.d/ with the matching DRIVERS field:

For the source’s RHEL/CentOS7 example, add the same historical parameter inside the existing GRUB_CMDLINE_LINUX string in /etc/default/grub, then regenerate the applicable configuration:

grub2-mkconfig > /boot/efi/EFI/redhat/grub.cfg

Install the correct rule under /etc/udev/rules.d/, correcting the source’s /etc/ude/rules.d typo, and perform the planned reboot/verification. These are historical Red Hat UEFI paths; CentOS/BIOS and other layouts differ. Verify the active boot configuration rather than overwriting an unrelated path.

B. Source PXE/Kickstart branches

The source edits /var/lib/tftpboot/pxelinux/pxelinux.cfg/efidefault to temporarily blacklist the external adapter’s actual driver, illustrating blacklist=mpt3sas. It names megaraid_sas and the misspelled PMC-driver alternative for other configurations:

That parameter’s recognition depends on the installer/version. Do not blacklist the driver needed to access the intended installation/root disk. Check the installed release’s dracut/Anaconda syntax and ensure the driver is restored in the installed OS.

The source’s RHEL6 Kickstart post-install template is reproduced with shell quotes/dashes normalized. URLs remain nonworking placeholders, not downloads:

%post --interpreter=/bin/bash
sed -i "s/blacklist mpt3sas/#blacklist mpt3sas/g" /etc/modprobe.d/anaconda.conf
sed -i '/module \/boot\/vmlinuz/ s/$/ rdloaddriver=ahci/g' /boot/efi/EFI/redhat/grub.cfg
sed -i '/kernel \/boot\/vmlinuz/ s/$/ rdloaddriver=ahci/g' /boot/efi/EFI/redhat/grub.cfg
wget -O /etc/udev/rules.d/18-scsi-sd-sequence.rules http://xxx/xxx/xxx/18-scsi-sdsequence.rules
%end

Its RHEL7 template is:

%post --interpreter=/bin/bash
sed -i 's/^GRUB_CMDLINE_LINUX="/&rdloaddriver=ahci /g' /etc/default/grub
grub2-mkconfig > /boot/efi/EFI/redhat/grub.cfg
wget -O /etc/udev/rules.d/18-scsi-sd-sequence.rules http://xxx/xxx/xxx/18-scsi-sdsequence.rules
%end

The source says to adjust the blacklisted driver and rule’s DRIVERS field to the actual card. The scripts assume exact file text, can append duplicate parameters and do not supply the missing rule; they are incomplete historical templates rather than a ready deployment fix. Confirm syntax, boot mode, rule availability and recovery access before adapting them. No exact public English counterpart for this OEM rule package was retrieved.

Sources

• https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/6/pdf/6.3_technical_notes/index63-technical-notes.pdf