What is /dev/cciss/c0d0p1

Recently I ran into issue to find out what is /dev/cciss/c0d0pX. Unfortunately, there was no direct and simple answer from the great Google.

This thing you can find in Linux OS where your partitions are mounted on  for eg. /dev/cciss/c0d0p2 instead on regular /dev/hdaX or /dev/sdaX. These are kind of "virtual disks" (/dev/cciss/c0d0) and are NOT regular hard disks (unlike /dev/hda or /dev/sda). Actually, these are RAID device configured from the BIOS or SmartStart CD before installing the OS. 

When you will try to install the Linux OS over such RAID configured from BIOS level, your OS will detect them as "/dev/cciss/c0d0" disks instead of regular "/dev/hda" or "/dev/sda". Although you can use them as your normal drives and create partitions, which will be called as “/dev/cciss/c0d0p1”, “/dev/cciss/c0d0p2”, etc, whereas your normal drives would have looked like “/dev/hda1”, “/dev/hda2”, etc or “/dev/sda1”, “/dev/sda2”, etc. You CAN use these partitions (/dev/cciss/c0d0pX) in your regular ways and can mount whatever you want, create LVM, etc.

Note: If you try to verify this "virtual disk" for RAID using # mdadm --detail /dev/cciss/c0d0 (or any other similar commands from the OS), it will return an error that it is NOT a RAID device. Thats b'coz the OS is not knowing about it, and it is configured beforehand installing the Linux.


/dev: You must be knowing what this directory is for.
cciss: These are the device types detected by Linux OS as Physical drives (The RAID which was created by your SmartStart CD).
c0d0: Controller #0; Disk #0 (similar to hda or sda)
c0d1: Controller #0; Disk #1 (similar to hdb or sdb)
.
.

c0d0p1: Controller #0; Disk #0; Partition 1
c0d0p2: Controller #0; Disk #0; Partition 2
.
.


Comments

  1. Those cciss devices don't appear in mount command output. Have you figured out how to associate c0dx with VolGroupXX ?

    Thanks

    ReplyDelete
  2. C0dx will NOT appear in mount command. The c0dx act like a normal DISK. mount command just displays the "partitions" which are mounted somewhere.

    You will have to create "Physical Volume(s)" like c0dxp1 and so on (as shown in diagram) over that c0dx. And then you can use those Physical volumes for VolGroupXX.

    If you already have c0dx created, you should be able to see it in the output of command "fdisk -l". If it is there, you can use pvcreate, vgcreate/vgextend commands to include that c0dx in your VolGroupXX.

    ReplyDelete
  3. Hi, can u tell me the steps to add my 2nd Disk ( /dev/cciss/c0d1 ) as Backup device in OpenVZ?
    I can't see it on my VZ control panel (Proxmox)

    Thanks

    ReplyDelete
    Replies
    1. If you have configured your 2nd disk ( /dev/cciss/c0d1 ) after virtualization, try rebooting...

      Delete
    2. i haven't configured, i tried these steps as i read s'where:
      root@server:/# mkdir /BackUp
      root@server:/# mount /dev/cciss/c0d1p1 /BackUp

      results i get below makes me think both the disks /dev/cciss/c0d0 & c0d1 are on Raid config, am i correct?

      root@server:~# mkdir /BackUp
      root@server:~# ls -l /BackUp
      total 0

      root@server:~# mount /dev/cciss/c0d1p1 /BackUp
      root@server:~# ls -l /BackUp
      total 136
      drwxr-xr-x 2 root root 4096 Apr 21 2011 bin
      drwxr-xr-x 3 root root 4096 Jun 13 08:23 boot
      drwxr-xr-x 3 root root 4096 Jun 13 08:22 cli-rt
      drwxr-xr-x 2 root root 4096 Jan 26 2010 dev
      drwxr-xr-x 61 root root 4096 Jun 16 03:41 etc
      -rw-r--r-- 1 root root 28158 May 10 2011 EULA
      drwxr-xr-x 2 root root 4096 Jan 26 2010 home
      drwxr-xr-x 14 root root 4096 Apr 21 2011 lib
      drwx------ 2 root root 16384 Jun 13 08:11 lost+found
      drwxr-xr-x 2 root root 4096 Jan 26 2010 media
      drwxr-xr-x 2 root root 4096 Jan 26 2010 mnt
      drwxr-xr-x 8 root root 4096 Mar 8 2011 opt
      dr-xr-xr-x 2 root root 4096 Jun 13 08:22 proc
      -rwxr-xr-x 1 root root 13229 May 10 2011 Read_Me_First.html
      drwxr-x--- 3 root root 4096 Jun 13 08:23 root
      drwxr-xr-x 2 root root 4096 Apr 21 2011 sbin
      drwxr-xr-x 2 root root 4096 Jan 26 2010 selinux
      drwxr-xr-x 2 root root 4096 Jan 26 2010 srv
      drwxr-xr-x 2 root root 4096 Jan 26 2010 sys
      drwxrwxrwt 3 root root 4096 Jun 25 17:30 tmp
      drwxr-xr-x 14 root root 4096 Apr 21 2011 usr
      drwxr-xr-x 22 root root 4096 Jun 13 08:22 var
      root@server:~#

      Delete
  4. You gave nice explanation of cciss here - I found it quite useful.

    ReplyDelete
  5. Nice blog about cciss!!1 thanks Adil for sharing !!

    ReplyDelete

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