Ubuntu

Trouble using IDE Raid on HP DL320 G2

Asked by Peter Magnusson

I am trying to install Ubuntu dapper or edgy on a HP Proliant DL320 G2 but with no success.

The DL320 G2 has a LSI Megaraid IDE raid itegrated raid solution and when trying to partition during installation it finds the 2 drives as separate drives hda and hdc not as the RAID 1 device I configured in the Megaraid BIOS.

The card is a CMD649 based one and that module gets loaded by the probing.
I know there has been issues with this before with earlier kernels but 2.6.17 supposedly has some megaraid drivers in it but it doesn't help much.

Hints, suggestions anyone?

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Alan Pope 🍺🐧🐱 🦄
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Alan Pope 🍺🐧🐱 🦄 (popey) said : 		#1

I suspect this device is a "fakeraid" device. See http://linuxmafia.com/faq/Hardware/sata.html#fakeraid for an opinion piece about fake raid.

It doesn't actually *do* hardware RAID, but uses the (when in Windows) driver to present one RAID drive to the Operating System.

Personally I would recommend you configure software RAID so that in the event that your controller/server dies you can pick the disks up and place them in another server (or even desktop) and you can access the data. You can also (in the event of one disk failing) easily replace a single failed disk in the set. Software RAID on Linux is incredibly flexible. The only downside really is that on hardware RAID there is the performance gain that the CPU isn't having to deal with this stuff. However in your specific case the hardware is a cheapo non-hardware RAID anyway, so you'd get no gain doing hardware RAID.

Hope that makes sense. Either way, have a google for fakeraid and linux and you'll find other opinions on it :)

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Alan Pope 🍺🐧🐱 🦄 (popey) said : 		#2

A friend of mine found this link which may also explain it:-

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=259927&admit=-682735245+1160043802774+28353475

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Peter Magnusson (kmpm) said : 		#3

I'm 100% sure that it is a "fakeraid" and I also know that doing software raid in Linux probably would be almost as good, but....

The RAID BIOS doesn't allow me to run with a unconfigured raidset (I havn't managed to do it anyway).
I know there is a megaraid driver that came with for example DELL PowerEdge 1600 that fixes the "raid" emulation so that linux think that is is a real raid device this driver is now suposedly integrated with the 2.6.17 kernel (might be called megaraid_legacy) and in my case with the annoying raid bios this would be a Ok solution.

If the megaraid driver solution can be ruled out by some reason, ok then but I would like to know not just guess.

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Peter Magnusson (kmpm) said : 		#4

I have found some troubleing information about the raid device. The information is for Windows but some of it apply to my situation as well.
I include this as a reference only so others might use the information as well.
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=491669

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Alan Pope 🍺🐧🐱 🦄 (popey) said : 		#5

Almost all IDE RAID devices are fakeraid. In fact I don't think I have ever seen one that isn't, although I'm sure they exist. They are targetted at the "budget" market so don't have the necessary RAID hardware on board, hence bodging it in software. Much the same way as Winmodems and GDI printers do.

I don't think that performance issue that you have found will affect you given one of the resolutions is a windows update which improves performance according to the poster.

Might be worth making sure the disks are on separate IDE channels whilst you're at it if performance is a real issue for you.

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Anthony Vickers (tattyheaded) said : 		#6

On my fakeraid device I configured 2 x 1+0 raid containers in the raid's bios, added a /boot+swap to the first device a swap to the second, then a linux raid partition on each with the remaining free space. I then added an md0 software raid container using the two linux raid partitions and put an ext3 partition on it mounted as /. Note the /boot is outside of the md0 container and I think that's the most important. Good luck.

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Peter Magnusson (kmpm) said : 		#7

My final solution was to do the following...
On the fa keraid configure 2 x RAID0 arrays. One for each disk.
Then I made i /boot on the first drive and a /swap on the second.
On the rest of the space I added a md0 software raid array. On that md0 device I assigned the whole lot to use with lvm and added a root partition using lvm.
It works, now I only have to get the fans slowed down...