Re: [gentoo-user] How to get raid

[Volker Armin Hemmann <volkerarmin@googlemail.com>]

Am Mittwoch, 4. Januar 2012, 21:28:32 schrieb Jeff Cranmer:
> On Wed, 2012-01-04 at 14:39 +0100, Volker Armin Hemmann wrote:
> > Am Dienstag, 3. Januar 2012, 21:57:18 schrieb Jeff Cranmer:
> > > Hi all,
> > > 
> > > I have recently built a new system, running Gentoo on a Sabertooth 990FX
> > > motherboard.  The board has a raid controller on which I'm running a
> > > 120GB solid state drive for the OS (Raid 0) and a set of three 1.5TB
> > > drives which were previously running as a RAID5 array.
> > 
> > no, it does not have a raid controller. It is bios raid. AKA fake raid.
> > You
> > will have less trouble if you stop using it.
> > 
> > google for mdadm. There are some very nice howto's.
> 
> Not sure I'd agree with you about the howtos being nice.  They mostly
> deal with trying to boot from a RAID array (don't want that, as I have
> my OS on a non-RAID 120GB SSD).  They're also contradictory, with some
> saying I need dmraid, and some saying not.  Most seem to make no more
> than a passing nod towards genkernel.

the short one:

partition one disk with (c)fdisk. Use sfdisk to transfer the partition scheme 
to the other disks.

run mdadm --create /dev/md0 level=whatever you want --raid-
devices=thenumberofdevices /dev/sdXY /dev/sdZY ... 

mdadm --detail --scan >> /etc/mdadm.conf

done


> 
> So, given that from the links that I've found, here's my starting set of
> questions.
> 
> In /etc/genkernel.conf, which options do I need to enable.
> One guide suggested the following settings
> DMRAID="no"
> MDADM="yes"
> MDADM_CONFIG="/etc/mdadm.conf"
> MDADM_VER="3.1.4"

there is a reason why I never ever touch genkernel.

you should forget that crap. You don't need to copy around anything. If your 
root is not on some fancy setup, you don't need initramfs.

Just make a nice kernel, put it in /boot. Done.

grub.conf:
kernel /vmlinuz root=/dev/sda1 nmi_watchdog=0

and you are fine.

Have the raids assembled by a) kernel (in that case you have to tell mdadm 
that on creation time, man mdadm is your friend) or by mdadm init script.

Don't use fakeraid. Set bios to ahci and be done with this.

the relevant part of Kernel config for example:

   <*>   RAID support                                                                                   
│ │  
  │ │                               [*]     Autodetect RAID arrays during 
kernel boot                                                    │ │  
  │ │                               < >     Linear (append) mode                                                                         
│ │  
  │ │                               < >     RAID-0 (striping) mode                                                                       
│ │  
  │ │                               <*>     RAID-1 (mirroring) mode                                                                      
│ │  
  │ │                               < >     RAID-10 (mirrored striping) mode                                                             
│ │  
  │ │                               <*>     RAID-4/RAID-5/RAID-6 mode                                                                    
│ │  
  │ │                               [ ]       RAID-4/RAID-5/RAID-6 Multicore 
processing (EXPERIMENTAL)                                   │ │  
  │ │                               < >     Multipath I/O support                                                                        
│ │  
  │ │                               < >     Faulty test module for MD                                                                    
│ │  
  │ │                               < >   Device mapper support                                                                          
│ │  
  │ │                                                                                                                                    
│ │  
  │ │

as you can see no dm support in my kernel.

No look what I got...

cat /proc/mdstat 
Personalities : [raid1] [raid6] [raid5] [raid4] 
md5 : active raid1 sdg2[2] sdf2[1]
      830278202 blocks super 1.2 [2/2] [UU]
      
md4 : active raid1 sdf1[1] sdg1[2]
      146479542 blocks super 1.2 [2/2] [UU]
      
md124 : active raid1 sdc1[2] sdd1[1] sdb1[0]
      64128 blocks [3/3] [UUU]
      
md1 : active raid5 sdc3[2] sdd3[1] sdb3[0]
      78123904 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
      
md2 : active raid5 sdc5[2] sdd5[1] sdb5[0]
      39069824 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
      
md127 : active raid5 sdc6[2] sdd6[1] sdb6[0]
      843813888 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

the numbers where once nicely 0-4 but some update fucked that up. No big deal 
- I mount by UUID. Something I strongly recommend.

-- 
#163933