Megaraid PERC 4/E is detected first, why ?

Richard Ford rford at
Mon Feb 12 04:10:55 CST 2007


I have never used a PERC5 and 4 in the same system.

Is this a new system install or trying to use the old data?

On one server I have with 2 x PERC4 (PERC4 DC and PERC 4eDC) the  
external array came in as SDB and the internal as SDA.

When I first did this though, it was reversed - but LVM picked it up  
and the system booted fine from SDB.

In my case the one bios util will control both cards - maybe this is  
not possible with a PERC4 and PERC5 paired together?

Are both cards in slots or is one a ROMB?  The other option is to  
swap the physical slots around so that one is read before the other  
by the BIOS....

On 12 Feb 2007, at 6:04 PM, Krishna Murthy, Elangovan wrote:

> Hi Richard,
> Thanks for your response,
> Yeah we have tried with the option as you said , i have selected  
> the PERC 5/i as first hard drive in the boot sequence menu and the  
> booted with my OS CD , but it shows /dev/sda as External array and / 
> dev/sdb as internal disk drives, And also i couldnt find the PERC  
> bios option as you said to control the two cards in one instance.
> Here we have two controller bios , one for PERC 5/i ( internal SAS  
> drive) and one more for external array i.e PERC 4E/DC , both have  
> BIOS enabled option.
> Thanks,
> Elango
> From: Richard Ford [mailto:rford at]
> Sent: Mon 2/12/2007 1:21 PM
> To: Krishna Murthy, Elangovan
> Cc: linux-poweredge at
> Subject: Re: Megaraid PERC 4/E is detected first, why ?
> This can be done in the BIOS.  Select boot order and SCSI card  
> order......I believe in the PERC bios which allows you to control  
> the two cards in one instance, you can also select which card (Or  
> virtual disk) is active for boot purposes...
> Also if you use LVM it should not matter and things will auto  
> adjust on the fly.  That is how I got all to work like this with a  
> PE1850 and PV220S....
> RF.
> On 12 Feb 2007, at 1:41 PM, Krishna Murthy, Elangovan wrote:
>> Hi,
>> We have 1950 system , in that one 5/I controller and 4 /E  
>> controller  with RAID-5 configuration,
>> We are facing problem in boot sequence , without connecting to the  
>> external array we have already installed OS on to the internal  
>> disk drives,
>> But we are facing problem after connecting back our external array  
>> to the 1950 system, show kernel panic error while booting up the OS.
>>  Its show external RAID array as /dev/sda and internal disk drives  
>> as /dev/sdb,
>> How to change the order of detection between PERC 5/I and 4/E  
>> ( external array ).
>> Thanks
>> Elango
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