Hi everyone,


Originally the system was running off of a single disk. For safety purposes i have cloned the system onto a raid mirror set. This set contains 2, 1tb disks. Once i have created the mirror, i used DD to clone the original disks onto the mirror.

When i tried to boot up off of the mirror set, i get to grub, start loading the OS, and it looks like its booting and it throws the volume group not found error.


specs : redhat 4, rocketraid 2642, dell poweredge.

Has anyone ran into an issue like this? Any clues may help.

Thanks in advanced, - pie.

I'm assuming you mean software RAID (mdadm metadisks)? You have to copy the master boot record to the second drive and also make grub entries for the second drive.

This post may useful:
http://lists.us.dell.com/pipermail/l...ly/008898.html

MensaWater,

Thanks for the quick reply. I am using a hardware array. Let me try and explain a little bit better.

Currently my system has three disks.

Disk A - 70gb has redhat isntalled. Uses volume groups.

Disk B - 1tb unpartitioned
Disk C - 1tb unpartitioned

I created a mirror using both disk b and disk c. The mirror was created using the bios utility. Once the mirror was created, i booted off of a live cd and ran DD to clone Disk A to the mirror. I then remove disk A by unplugging it from the system. Once removed, i try and boot off of the mirror. Booting off of the mirror is unsuccessful and throws the error 'volume group not found, kernel panic'

However, when i degrade the mirror and try to boot off of Disk B or C as a single disk, it boots fine.

So your system can see both disks B and C? If so then it isn't a true hardware RAID but rather "fake RAID".

Have a look at this Wikipedia definition:
http://en.wikipedia.org/wiki/RAID#Fi...ver-based_RAID

Doing some searching for Fake RAID may lead you to an answer. Some of what I saw said that since the CPU has to do the work as it does in software RAID why bother with the fake raid - just use the software RAID. I did see some hits for RHEL4 and Fake RAID that might be useful.

I also saw a Fake RAID Howto for Ubuntu which wouldn't directly apply but might give you some ideas for what you need to do. Where it talks about apt-get you'd use up2date instead.
https://help.ubuntu.com/community/FakeRaidHowto

MensaWater,

The system is using RocketRaid 2642 a PCI Raid Controller. As far as i know, its not fakeraid. Also, after i created the mirror using the bios utility i could only see two disks /dev/sda and /dev/sdb ( mirror )

To clone, i used dd if=/dev/sda of=/dev/sdb


-Pie

I have a number of RocketRaid controllers we use at work. They are all fakeraid. What's worse is I haven't been able to find any current linux drivers (one is available for old kernel versions.) I haven't bothered with trying to compile one for quite some time as they work just fine as an HBA adapter that the kernel can use the bare drives from. If you've got a RocketRaid card running in linux correctly then that's great, but I question weather you'll be able to boot from it.

1 members found this post helpful.

This post says RocketRaid controllers except for 3000 series ARE fake raid.

http://forums.opensuse.org/archives/...ml#post1597792

If it were REAL RAID you would not see both drives at the OS - you'd see a single drive which is the RAID set rather than either of the individual drives. We use Dell PERC in our Dells (which is an OEM of LSI Controllers) which are REAL RAID so whether we do RAID5 or RAID1 (mirroring) we see oly a single disk for each RAID set.

If the disks are detected by the kernel why wouldn't one be able to boot from one of them? Or for that matter put them in under mdadm software RAID mirroring? (Not arguing - just asking for curiosity's sake.)

I believe the system views the mirror as a single drive. When i cloned the original disk to the mirror i only saw /dev/sdb. I have a feeling this isn't an issue with the raid controller but with the volumegroup itself.



travisdh1, "I question weather you'll be able to boot from it."

I can boot from the mirror set. I see grub and it gives me some boot options. Once i select an OS from Grub, it starts to boot up and everything is normal until it tries to find the volumegroups.

Sorry for the double post but i found a readme in the driver install directory and i found this :


1) Booting problem after drive configuration changed

If you add or remove drives after OS installed, Linux may have problem to
boot since the device name will change. To solve this problem, first get the
correct device name on which the root file system resides, then type "linux
root=/dev/sdx" (where sdx is the device name) at "LILO:" prompt (if the booting
screen is graphic mode, press Ctrl-X to enter text mode first; for GRUB users
just append "root=/dev/sdx" to the boot string). After you boot into system you
can modify /etc/lilo.conf to use the correct root device.

2) OS device name may change after drive configuration changed

OS device name may change when you add or remove drives after OS installed,
or after you rebuild a broken array with existing single drive. In this case if
you have statically configured device names (E.g, in file /etc/fstab), OS will
have problem. You must modify the configuration files to solve this kind of
problem. Please refer to "device mapping order" in above section to get the
device name for each logical device, then modify the configuration files.

/dev/sdb would be the second drive. What does "fdisk -l /dev/sda" and "fdisk -l /dev/sdb" show?

When I'm talking about seeing a "single" drive I mean seeing only one drive as opposed to seeing two separate drives. If you have an sdb it suggests you also have an sda. That is to say seeing the "mirror" as sdb doesn't mean you are NOT also seeing the "primary" as sda. If you are seeing both sda and sdb for the two drives (assuming there are only two physical drives) then you ARE seeing both drives and it IS fake raid. "Real" RAID would only show you one drive for the RAID set (i.e. either /dev/sda or /dev/sdb but not both). If you have more than one RAID set then each set would be seen as a drive. (That is if you had 7 physical drives and put two in a RAID1 mirror and the other 5 in a RAID5 set then the OS would see 2 drives - one for the RAID1 and one for the RAID5.)

Prior to going down the path suggested by what you found in the README you really need to determine if you're seeing both physical drives or only one RAID set presented as a single drive. Your earlier post and reading on RocketRaid suggest you are seeing both physical drives and are therefore doing FakeRaid.

MensaWater,

Sorry for the confusion. /dev/sda was the original disk in the system. Its a 70gb disk and it has nothing to do with the mirror. The mirrored disks show up as /dev/sdb