2 SCSI Controllers

[Jeff Vian]

Götz Reinicke wrote:

>
>
> Alexander Dalloz schrieb:
>
>> Am Do, den 29.04.2004 schrieb Götz Reinicke um 12:07:
>>
>>
>>> Hi,
>>>
>>> I have an Dell PE 1650 Server with an internal perc 3/di SCSI RAID 
>>> Controller hosting a RAID 1 and an Adaptec 29160 Controller hosting 
>>> an external Hardware RAID-Box.
>>>
>>> If I boot, and try to install Fedora, the external RAID is seen as 
>>> sda, the internal RAID as sdb.
>>>
>>> How can I change this order, so that the internal RAID is sda and 
>>> the external RAID is sdb? Any ideas?
>>>
>>>
>>> Regards
>>>
>>> Götz Reinicke
>>
>>
>>
>> Just change the SCSI ID of the RAID arrays/drives. The lowest is sda,
>> the second... Remembering your previous post about difficulties with an
>> external SCSI driver array of SATA drives I guess you can specify the
>> SCSI ID for the whole external box.
>
>
> I do have different IDs, 0 for the internal RAID, 1 for the external 
> RAID-Box. The later is attached to a different SCSI Controller.
>
> But the external Box is seen as sda :-(
>
This is because of the sequence in which the cards are seen/configured 
on the PCI bus, as well as the scsi bus ID sequence.  The scsi ID is not 
the only thing it looks at to decide what name it gives the drive.

The general rule to decide what device gets what name is first 
configured controller, scsi id sequence on that bus,  then next 
configured controller, scsi id sequence on that bus,  etc.

Thus, you can have a controller in pci slot 1 and another in slot 3.  If 
the controller in slot 3 is configured first its drives take precedence 
over those on the controller in slot 1.

If you have devices on  a single controller, AFAIK they will always get 
configured in id sequence.
This can become a problem if you leave gaps in the scsi IDs then later 
add another device that fills that ID slot. the drives at the later IDs 
will get the name changed.  

For example, you have a single scsi drive at ID 4.  this will by default 
be named sda.  Then you add another drive at ID 0.  Now that new drive 
will be sda and the original becomes sdb.  This effect can be a bit 
disconcerting at times if not expected.

>
> so long...
> ...Götz