Linux RAID setup

Linux RAID setup

[Poonam Dalya]

 Hello Sir,

         I want to Setup RAID 0 on my standalone
system. I have windows and linux both on my system. I
went through many documents and and also through the
book 'Managing RAID on Linux ' by Derek Vadala. I
tried to setup RAID with the following steps. I
downloaded mdadm from your site. I have listed down
the steps i did with their outputs. Please if you
could go through it and let me know where the problem
lies, it would be of great help.
 
 1. I was able to include the RAID modules with the
 modprobe command. The mdstat file was as below.
 
 bash2-2.05b# cat /proc/mdstat
 Personalities : [raid0] [raid1]
 read_ahead not set
 unused devices: <none>
 
 ---------------------------------------------------
 
 2. I partitioned the disk using fdisk and the
 pratition table looked like below
 
 Disk /dev/hda: 40.0 GB, 40020664320 bytes
 255 heads, 63 sectors/track, 4865 cylinders
 Units = cylinders of 16065 * 512 = 8225280 bytes
  
    Device Boot    Start       End    Blocks   Id 
 System
 /dev/hda1   *         1      1275  10241406    c 
 Win95 FAT32 (LBA)
 /dev/hda2          1276      2550  10241437+   f 
 Win95 Ext'd (LBA)
 /dev/hda3          2551      2626    610470   82 
 Linux swap
 /dev/hda4          2627      4865  17984767+  fd 
 Linux raid autodetect
 /dev/hda5          1276      2550  10241406   fd 
 Linux raid autodetect
  
 ------------------------------------------------
 
 3. Then I worrked with the following command.
       I got the following error.
 
 bash2-2.05b# mdadm --create /dev/md0 --level=0
 --chunk=128 --raid-disks=2 /dev/hda5 /dev/hda4
 mdadm: /dev/hda5 appears to contain an ext2fs file
 system size=10241404K  mtime=Sat Oct  9 17:06:24 2004
 Continue creating array? y
 mdadm: ADD_NEW_DISK for /dev/hda5 failed: Invalid
 argument
 
 --------------------------------------------------

 4. When i again tried with that command, it showed
 the following error.
 
 bash2-2.05b# mdadm --create /dev/md0 --level=0
 --chunk=128 --raid-disks=2 /dev/hda5 /dev/hda4
 mdadm: /dev/hda5 appears to contain an ext2fs file
 system size=10241404K  mtime=Sat Oct  9 17:06:24 2004
 Continue creating array? y
 mdadm: SET_ARRAY_INFO failed for /dev/md0: File
 exists
 
 ---------------------------------------------------

 5. the mdstat file was same 
 
 bash2-2.05b#  cat /proc/mdstat
 Personalities : [raid0] [raid1]
 read_ahead not set
 md0 : inactive
 unused devices: <none>
 
        Please if you could solve my problem, it
 would be of very great help for me. I have a deadline
as sunday and today is saturday. So, sir please do
 reply.
         Thank you.
 
 With Regards,
 Poonam
India.
 
 
 		
 
 



		

Re: Linux RAID setup

[Neil Brown]

On Saturday October 9, poonamsbox@yahoo.com wrote:
>  
>  3. Then I worrked with the following command.
>        I got the following error.
>  
>  bash2-2.05b# mdadm --create /dev/md0 --level=0
>  --chunk=128 --raid-disks=2 /dev/hda5 /dev/hda4
>  mdadm: /dev/hda5 appears to contain an ext2fs file
>  system size=10241404K  mtime=Sat Oct  9 17:06:24 2004
>  Continue creating array? y
>  mdadm: ADD_NEW_DISK for /dev/hda5 failed: Invalid
>  argument

Are there any messages from the kernel at this time.  
The command
   dmesg

would show them..

However my guess is that you only recently created these partitions.
You might need to reboot before they are recognised.

>  
>  --------------------------------------------------
> 
>  4. When i again tried with that command, it showed
>  the following error.
>  
>  bash2-2.05b# mdadm --create /dev/md0 --level=0
>  --chunk=128 --raid-disks=2 /dev/hda5 /dev/hda4
>  mdadm: /dev/hda5 appears to contain an ext2fs file
>  system size=10241404K  mtime=Sat Oct  9 17:06:24 2004
>  Continue creating array? y
>  mdadm: SET_ARRAY_INFO failed for /dev/md0: File
>  exists

Yes, you need to stop the array
  mdadm --stop /dev/md0
because it is half-created.  But a reboot will achieve the same
effect.

>  
>         Please if you could solve my problem, it
>  would be of very great help for me. I have a deadline
> as sunday and today is saturday. So, sir please do
>  reply.
>          Thank you.

If the above doesn't help, send us the complete output
of 
   dmesg
immediately after failing to create the array.

NeilBrown

Re: Linux RAID setup

[Bernd Fischer]

Poonam Dalya wrote:

>  3. Then I worrked with the following command.

>  bash2-2.05b# mdadm --create /dev/md0 --level=0
>  --chunk=128 --raid-disks=2 /dev/hda5 /dev/hda4

Are you sure about that? You are trying to create a RAID0 array using 
two partitions on the same physical device. This will result in abysmal 
performance, which is exactly what you don't want.


Bernd Fischer