News Group Posts

raid controllers

From: "Brian K. White" <brian@aljex.com>
Subject: Re: SCSI Tape Drive
Date: Thu, 19 Jun 2003 13:11:33 -0400
References: <3EEF9E15.1D4A2F0@canada.com>
<4mcvevggf1uf7kqt3gigh5r4bt7ai2d9bs@4ax.com>
<3EF07F11.8DA4ADB4@canada.com>
<r001fvclt2p71plihl5tbdvk22b5kniqhq@4ax.com>
<3EF08D63.CBC73F91@canada.com> 

On Wed, 18 Jun 2003 17:03:50 +0000, Skot wrote:

> 
> Scott McMillan wrote:
>> 
>> On Wed, 18 Jun 2003 15:02:43 GMT, Skot <skot@canada.com> wrote:
>> 
>> 
>> >Scott McMillan wrote:
>> >>
>> >>
>> >> Also note:  I DO NOT recommend placing a tape drive onto any RAID
>> >> controller!)
>> >
>> >Don't think you could on this OS, doesn't seem to recognize the second
>> >channel anyway.  But why not anyway?  What's the use of a second
>> >channel if you shouldn't use it?
>> 
>> Because RAID controllers are meant to control hard drives, and many
>> won't support tape/CD drives at all.  Has nothing to do with the OS in
>> those cases.
> 
> Hmm... Makes sense, somewhat.
> 
>> So what is the model of this controller?
> 
> That's not so clear, it's an onboard thing, ServeRAID-4 Ultra 160 I
> think, on a xSeries 225, Type 8647.  Not that it matters, the question
> was how to get the OS to recognize the second channel, the hardware is
> setup fine.
> 
> 
>> >BTW, 'sconf' does not show the second channel either.  hmm...
>> 
>> Maybe it's been disabled by the (controller/system) BIOS?  I remember
>> many Dell systems that shipped with their embedded 29160 with the 1st
>> channel enabled, 2nd channel disabled.
> 
> It's not Dell, it's IBM and the Controller is the first controller it
> has 2 Channels and both channels are active, the second channel even
> shows the tape drive connected.
> 
> Well, regardless, I'm putting a second controller on there, now I have a
> choice between an Adaptec 29160n and a newer IBM PCI Ultra 160, both
> apparently work with OSR5.  Now how to add the second controller...
> That, I've done before.

You are asking the wrong question.

If it's a raid controller, then often the actual hardware is hidden from
the OS and only virtual hardware is presented to the OS. You use the
second channel by plugging half of your drives on it (even if there is
only two drives total) and in the raid card's bios you reconfigure the
raid array to span both drives. The OS still only sees one drive on
channel "0"

Different raid cards use different schemes for showing the OS more virtual
drives after the first "0,0,0,0" drive.

In some cases you add another drive anywhere you want physically, any
channel, any scsi id, and to the OS that new drive just looks like
channel=0 id=0 lun=1

more often the lun is always 0 and the id increments with each new drive.

and sometimes there is an option to access a physical location by it's
real channel/id/lun as long as it doesn't happen to conflict with any
existing virtual drive.

You may have to tell the card's bios that a drive is there and that it is
active/enabled even though you don't configure it into some array, or you
may have to define an "array" that only has one drive. It might simply not
be possible to use a tape drive because as has been mentioned, sometimes
the raid card's bios simply only recognizes disk devices, not any old scsi
device.  (/me contemplates an array of scanners...)

-- 
Brian K. White  --  brian@aljex.com  --  http://www.aljex.com/bkw/
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filePro BBx  Linux SCO  Prosper/FACTS AutoCAD  #callahans Satriani

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