What is dual active raid controller

Posted on 2007-08-03
Last Modified: 2013-11-14
Some please tell me what does it mean for a RAID controller to be dual active.
I have noticed partitions on my Compaq DL380 server automatically move from /dev/cciss/c0d0 to /dev/cciss/c1d0.
Could it be done by RAID controller as a failover?
Question by:lalit_expert
    LVL 55

    Expert Comment

    It is being done by two RAID controllers (c0 and c1) so you must have some external storage that is dual-attached, MSA500 or a SAN are likely.

    Author Comment

    There is only one dual channel controller, with 4 scsi disks forming RAID 5. 3 disks are active members and 1 is hot spare.
    The partitions used to mount till recently on c0d0p1, c0d0p2 and likes.
    Now they mount on c1d0p1, c1d0p2 and likes.
    The problem was discovered when the SWAP went missing as the SWAP partitions were still mentioned to be on c0d0 in fstab.
    fdisk /dev/cciss/c0d0 reported unable to read device. But the OS was running. It was later found upon running fdisk -l /dev/cciss/c1d0 that the partitions have moved from channel 0 to channel 1.
    LVL 55

    Accepted Solution

    HP Smart Array controllers can't swap channels on their own except for the case of dual controllers on a MSA500 so I suspect someone swapped the wires over. I suppose it's possible that c0d0 is a rogue device under software and a new c0d1 was created with the correct hardware settings to attach to the physical device that c0d0 used to point to but that's too deep into your OS for me to be sure.

    There certainly isn't something called a dual active RAID controller although both channels are actice on a normal dual channel controller.
    LVL 1

    Expert Comment

    Forced accept.

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