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Old 05-13-2004, 03:04 PM   #1
erlend
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Linux Software Raid & Dual Boot


I have a Promise FastTrak software raid card with BIOS support. I have a Windows/Linux dual-boot system using the proprietory raid module from Promise. I want to upgrade to the 2.6 kernel, and use the GPL libata (sata_promise.o) driver by Jeff Garzik, however I have read in several places that Linux Software Raid (md) cannot be used on disks where there is a dual-boot. Is this true? Can anyone tell me why please?

Thanks,

Erlend
 
Old 05-19-2004, 08:33 PM   #2
Road
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I don't see why not, it just depends on what partitions you mirror. Making it bootable might be a little tricky but thats about it.
 
Old 05-19-2004, 11:31 PM   #3
finegan
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Technically, this is Hardware RAID, true that the kernel and software are doing all the work, but what you're reading about refers to true Linux software raid, a /dev/mdX situation...

Also, I would be careful as the GPL module and the promise driver treat the array as different devices: the GPL I think is going to end up being /dev/ataraid/p0d0 while the promise driver creates it as /dev/sda1

Cheers,

Finegan
 
Old 05-20-2004, 02:41 PM   #4
erlend
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Thanks for your replies.

ataraid no longer exists in the 2.6 kernel for the time being. I have heard it will be ported soon, except as part of some device-mapper thing (I don't understand anything about this device mapper, I would like to find out a little more). I don't think libata will ever do ataraid, but other modules (device-mapper) will sit on top and do the raid.

Quote:
I don't see why not, it just depends on what partitions you mirror. Making it bootable might be a little tricky but thats about it.
I installed Mandrake 10 on to an extended partition on the first of my two disks in the array, install went ok, but i can't boot it (grub). Something about not being able to find vmlinuz, or non-executable format. I think this is because the bios is doing a disk-spanning trick which makes the drives look raided (it does this for booting windows, and then turns to software raid), and so it wouldn't see just one disk but two (hence filesystem appears corrupt). I was wondering if it might be possible to have /boot on a proprietory-raid partition, and / on md raid (at least until I find out more about the device-mapper ataraid)?

Thanks again,

Erlend
 
Old 05-21-2004, 01:27 AM   #5
finegan
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I honestly don't know... I've built software raid0 with the array being the boot device, and raid5 and raid1, but I always kept a spare /boot partition off the array. I've done hardware raid0,1,5,10 with these horrid little PATA cards and its worked out fine... offhand, I don't think the kernel would be able to see the physical drives as seperate (for mdX software raid), and at the same time as 1 logical drive in hardware raid for the boot partition. Its a bit of a mess really.

Personally, I blame grub...

I've done the hardware raid thing with 3ware cards, Promise cards (old ones... PDC20267 etc...) Highpoints, and adaptecs, and not seen the loader hork unless it was Grub.

If you can boot-disk you way into the Linux partition, might want to fiddle with Grub options... or just give lilo a whirl.

Cheers,

Finegan
 
Old 05-21-2004, 03:13 AM   #6
erlend
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Quote:
I don't think the kernel would be able to see the physical drives as seperate
My idea (which is probably crazy) is that the kernel would only be able to read mdX partition - i.e. it would not be able to read itself, the bootloader can read it and start it and for new kernel builds I would have a proprietory-raid based installation which can read /boot.

Quote:
Personally, I blame grub...
Would it be better to use lilo for something like booting off a single disk of an array when the bios is trying to stripe them?

Thanks,

Erlend
 
Old 05-21-2004, 04:46 AM   #7
finegan
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Quote:
Originally posted by erlend
My idea (which is probably crazy) is that the kernel would only be able to read mdX partition - i.e. it would not be able to read itself, the bootloader can read it and start it and for new kernel builds I would have a proprietory-raid based installation which can read /boot.


Actually that's quite true... the MBR is just the first 512 on the first disk in the array, if it ignores the hardware array then it should be alright... I can't remember if you can boot to a raid1 root yet... back when I built my soft raid5 2 years ago you couldn't and had to have at least /boot on a seperate partition.

Quote:
Originally posted by erlend

Would it be better to use lilo for something like booting off a single disk of an array when the bios is trying to stripe them?

Thanks,

Erlend
Yeah, that would be easier... I really am giving Grub a lot of crap it doesn't deserve, Lilo is just so blindly stupid and simple it appeals to my inner moron.

Cheers,

Finegan
 
Old 05-21-2004, 01:01 PM   #8
erlend
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Another potential problem with md on dual-boot is that windows is raided across the same two disks... There is no partition table on the second disk, but for md there would need to be one - wouldn't putting a parition table on the first disk mess windows up a bit?

I have heard about a device-mapper module replacement for ataraid in the 2.6 kernel, which could help for emulating proprietory-raid partitions. I don't know anything else about it, not even sure if it exists yet. Do you know where I can find out more? I've read the how-to on lvm and lvm2 but they don't really help that much.

Thanks,

Erlend
 
Old 06-08-2004, 11:25 AM   #9
vlado04
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Hi!

Is it possible to do dual boot between Win XP and Fedora Core 2 if using RAID 0? I have RAID on my Intel Bonanza motherboard (875 chipset). It seams that Fedora does not recognize RAID (.. i have installed Win XP first with RAID 0, and that works).

Any pointers?

Please?
 
Old 06-08-2004, 01:12 PM   #10
erlend
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Need more information really - what raid chip are you using?

I assume you are using a software raid setup (that includes the quasi-hardware raid cards), if so then you will need a driver (if you needed to insert a disk driver to install WinXP you probably have software raid). Getting a driver for your raid card to work in linux in the next step: you'll need to find out what your raid chip is.

If you are using SATA raid, the following will be of interest:
http://www.linuxmafia.com/faq/Hardware/sata.html


Erlend
 
Old 06-08-2004, 07:44 PM   #11
abstractius
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cardless ide raid 0/1

I can confrim that dual booting with the md devices is no prob, in fact a few HOWTOs say you'd need LILO but I was able to install grub too. I used Suse 9's and 9.1's "install in software RAID" option, so I didn't have to work hard to setup the devices. It goes without saying that this setup leaves the Windows partition(s) unRAIDed, and SuSE's installer does not by default install the boot loader on both drives. So if the wrong one dies (like mine) you're left trying to figure out how to boot the thing and rebuild the RAID. I'm on the verge of asking for help with this, but I expect it to be unexciting
 
Old 06-09-2004, 02:33 AM   #12
vlado04
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Thanks Erlend!

I guess that Intel has integrated RAID logic directly into its Southbridge controllers (http://www.gamepc.com/labs/print_con...ookie%5Ftest=1) but it seams like quasi-hardware raid coz i needed SATA RAID disk driver to install WinXP.

The problem is that i cant install linux (Fecora Core 2 with integrated SATA raid support) in dual boot system (Win XP+Fedora Core 2).

What should I do? If I install Linux first, Win XP cant recognize partitions and viceversa. I hope that I will not have to disable RAID.

HELP! Please!
 
Old 06-09-2004, 08:28 AM   #13
erlend
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How can you not install Fedora? Error messages? Does the installer not see the disks? Is it saying the partition table is corrupt? Is it installing and then not booting?

Quote:
Fecora Core 2 with integrated SATA raid support
How do you know it has built in SATA raid support? The reason I am asking is that there are different drivers for different chips. I suspect you need libata (it is intel raid-onboard right?), which may be built into the Fedora project's kernel. ata_piix is the driver within the libata project for the Intel ICH5/ICH5R family of onboard controllers. Basically if the installer is seeing the drives (separately - sda/sdb or hda/hdb) you don't need to know any of this. If not, Fedora probably doesn't have support for your controller.

Seeing the disks separately isn't going to help all that much. You need to install to them as RAID0, and the raid on both your windows and linux partitions has to be the same. There is a driver (http://lwn.net/Articles/60247/) called iswraid which will create the intel-type raid partitions, and allow windows and linux to coexist both as raid0, but I think it is only for the 2.4 kernel (fedora C2 uses 2.6).

If I were you, I think I would get hold of Fedora Core 1 (which uses the 2.4 kernel), and install that in the time being. Once you have a working Fedora on the drives you can compile yourself a 2.6 kernel and upgrade.

Hope this helps,

Erlend

PS: there is a new development in these proprietory software raid setups - raiddetect; basically it's a userspace program which you can patch into udev and by sticking it in your initrd it will detect the raid you are using, and set up raid itself via dm (device-mapper). If you want more information go to: http://www.hailfinger.org/carldani/l...es/raiddetect/ or search google for "raiddetect".
 
Old 06-09-2004, 09:20 AM   #14
vlado04
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Thanks Erlend (again !

Fedora recognizes my ICH5 onboard controller (its driver loads before Anaconda) but unfortunately Anaconda (and Disk Druid) does not recognize my RAID0 created by Windows XP and its partitions (i.e. it says something like that it cant recognize my disks)!

I can create a new RAID0 with Disk Druid but unfortunately that fries Win XP and its partitions.

If I install first Fedora Core 2 with RAID0 then Win XP does not recognize anything on my disks..

Vlado
 
Old 06-09-2004, 01:05 PM   #15
erlend
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Ok, you've actually got much the same problem as me! The linux raid0 (which fries winxp) is md basically. The linux software raid isn't compatible with the proprietory intel raid. Before you can go any further you need either:
1. An installer with raiddetect built-in, which will take a while (if ever - the program it very new).
2. A working linux (2.4) installation, so that you can setup dm.

You could try and install fedora core1 - I think it will work.

Erlend
 
  


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