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Our HP Proliant ML150 is configured as RAID in the BIOS, and created a "Logical drive" (using two 250GB HD) as RAID 1+0.

The procedure seems to be Ok.

However, when installing the OS (Ubuntu 10.10) the partitioner utility still shows our two HD

  /dev/sda
  /dev/sdb

I was expecting to see only one drive, since the two HD are RAIDed.

Is there a special step missing (checked again at boot, the RAID logical drive is still alive)?

edit It seems Ubuntu does not recognize the logical RAID drive.

edit2 RAID 1+0 is possible with two disks. See this Wikipedia page.

  RAID 1+0: mirrored sets in a striped set (minimum two disks but more commonly four disks to take advantage of speed benefits; even number of disks)
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You want 4 disks to do 1+0 right. With 2, just do raid 1. –  Joel Coel Dec 7 '10 at 4:22
    
There is no "1" raid, only "1+0". And there should not be any problem with that. –  ring0 Dec 7 '10 at 4:24
    
The ML150 comes with a software raid onboard (aka, fakeraid). The windows driver picks that up and mirrors the two drives. Non-Windows systems show two independent disks. –  Chris S Dec 7 '10 at 13:32
    
Actually there are drivers for Redhat and Suse provided by HP on their site. –  ring0 Dec 7 '10 at 15:53

3 Answers 3

up vote 2 down vote accepted

Either get a hardware RAID controller like a SmartArray P4xx or use software RAID. SW RAID works well on Linux - much better than Windows - so you may not need HW RAID.

The main advantage of HW RAID is battery backup which gives you a fairly good chance of surviving a power outage without corrupting your disk. You might find it worth your while to get a HW RAID controller for this reason.

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Thanks - this is what we'll be doing, Ubuntu's software RAID. –  ring0 Dec 7 '10 at 13:23

Ubuntu doesn't recognise the RAID logical drive created by the BIOS.
And no driver is available.

  Ubuntu is not supported by HP for the B110i Smart array RAID controller Proliant ML150 (G6)

So our choices are down to

  • install another OS
  • use the software based RAID
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+1, Also 3rd choice is to pickup a real RAID card like the P4xx series. –  Chris S Dec 7 '10 at 13:34

It is impossible to implement fully functional RAID 0+1 using only 2 hard drives (refer to the RAID guides, for example here http://www.bjorn3d.com/read.php?cID=886). It is pointless to use RAID 0 without getting any advantage in speed and capacity, also using RAID 0 is no option for the server, because if one disk fails - you loose all the data you have. So there is few options:

  1. To buy 2 more HDDs, similar to the ones you already have and build normal RAID 1+0
  2. Just not to use RAID
  3. Use software RAID (read more here: https://help.ubuntu.com/community/Installation/SoftwareRAID)
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It is possible - see my edit2. Take a piece of paper, draw the disks and imagine that without any speed advantage you can get 1+0. The HP Array does not have 1 anyway, only 1+0. –  ring0 Dec 7 '10 at 13:23
    
The BIOS in those servers says 1+0, if you use two drives you'll get just RAID1; if you have 4 or more you'll get 1+0. –  Chris S Dec 7 '10 at 13:33
    
Made a little edit –  Alexey Shatygin Dec 8 '10 at 0:38

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