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Linux on Integrity servers with EFI software RAID 1 partition

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Venilton Junior
Valued Contributor

Linux on Integrity servers with EFI software RAID 1 partition

Hello guys,

I was wondering and googling for this information but couldn't find some information that answered my doubt.

We have an old rx2620 with no SmartArray controller and want to use it. So, I have to install a RHEL AS v4 with software raid, using md devices.

I wonder if is it posible to put the FAT32 EFI partition in this type of RAID.

I was talking with an HP expert and he told me that it works with some restrictions and advise me to not use this. HP only recommends to use this kind of mirroring with HP-UX and OpenVMS.

Does anyone have experience with this? Any ideas if this could or not work?

Tnx for now

Occasional Visitor

Re: Linux on Integrity servers with EFI software RAID 1 partition


Sorry I don't have a handy document to point you to but I have done this setup a long time ago with a Debian system. RedHat shouldn't be different for this issue.

The quick answer is "No, one cannot put the EFI boot partition under md control.", however....

The bootloader on an EFI/Itanium system is elilo. The boot partition (as you've discovered) is a FAT formatted GPT partition with a different directory tree for each OS which boots off of that partition. Entries are created in the EFI boot menu that point to each boot partition's OS choice.

So the basic strategy is this:
1) Have two disks on preferably separate SCSI busses. Partition them manually (ie in advanced installation screens) so they each have a GPT partition that will eventually be used for boot and another for root.

2) Install OS as normal with the root partition setup for RAID 1 (doable through the installation screens). Only one boot partition is in use at after initial install.

3) Change your elilo config file to NOT specify which partition is the boot partition. From now on, manually update the boot partitions by using the "-b" option to elilo. So something like "elilo -v -b /dev/sda1; elilo -v -b /dev/sdb1". This also means that updates affecting the elilo installation will fail which is GOOD so it reminds you that this has to be done manually.

4) Create two EFI boot menu options each pointing to their respective boot partition. Set a timeout for the first one and so it will fall through to the second.

This all works fine enough but there are issues. Elilo is an error prone manual process in this case (a long time ago I put in a request to handle multiple boot partitions in the configuration file). The mode of failure of the first EFI menu item might prevent EFI from timing out.

This highlights some of the beauty of having a good, embedded hardware raid controller (eg SmartArry) for avoiding administrative hassle.

I hope this helps.
Venilton Junior
Valued Contributor

Re: Linux on Integrity servers with EFI software RAID 1 partition

Tnx for the whole explanation of what have you done.

This help me out a lot.

I know that the best option is to have a SmartArray controler, but in this rx2600 we had HP-UX running with HP-UX. That's why I've asked about mirroring by software.