Install on Dell PowerEdge w/ RAID 5

[scottprive at earthlink.net (Scott Prive)]

----- Original Message -----
From: <trlists at clayst.com>
To: <discuss at blu.org>
Sent: Saturday, March 01, 2003 12:38 AM
Subject: Install on Dell PowerEdge w/ RAID 5


> I am trying to install Slackware 8.1 on an older Dell PowerEdge server
> (4100).  There are two SCSI controllers in the server, an on-board
> Adaptec 7860 driving the local drives and a 7880 in a PCI slot driving
> the RAID.  The RAID array is 4 9gb SCSI drives in a RAID 5 array, set
> up to look like one 27GB drive.
>
> I am starting from a boot disk with adaptec drivers and I see both
> cards recognized during boot.  The SCSI CD-ROM tied to the on-board
> controller is also recognized though I haven't tried to mount it yet --
> but it finds the drive brand, ID, etc.
>
> My problem is that the RAID drives seem to disappear.  Or maybe they
> are there but I don't know where to look.

You don't mention, so I assume you're using 'raidtools' (and a recent one at
that, like 0.90 or 1.x?).
An alternative to 'raidtools' is 'mdadm'. Configuration and troubleshooting
in mdadm is (supposedly) more straightforward. I'm preparing to build a RAID
on my linux tower using mdadm so I can answer some of your questions, but
not all of them.

Not sure what you mean by "disappear", but you can have problems if your
RAID partitions don't have superblocks (you CAN run RAID without them, but
not advised).

Also, if you dedicate a whole disk as a RAID partition, the kernel won't
autoinitialize the RAID. Example: you use 'sdb' and 'sdc' as a simple RAID-1
mirror, it would not autoinitialize (however if you allocate all space on
'sb{b,c}' to a single partition, it WILL autoinitialize... don't ask me why
:-)

>  Should I see them as sda?
> md0 (or is that only for software raid)?

Yes, md* is software raid (or a hybrid raid...but md indicates a software
layer is involved), but you'd always see the sd?? partitions as devices.

>  Something else?  Is there a
> different set of names for the drives on a second scsi controller?  sda
> is not even in /dev.

That would be a problem. No idea how THAT could happen (flakey kernel
module??)

>  Or do I have to do something special to get the
> kernel to see these drives?  I'm sort of assuming not, as they should
> just look like one big SCSI drive to the kernel.

A functioning RAID looks like one block device to the kernel; it doesn't
appear as SCSI (IDE, firewire etc.). The underlying components (like sda, or
sda1, hda1 etc) should always exist as a device.

Hope this sheds a little light even though I couldn't get them all.

Highly reccomend getting "Managing Linux RAID" from Oreilly books. It just
came out this year, and it beats reviewing all scattered bits of how-to's.
Bookpool has stock.


>
> Thanks for any help.
>
> Tom
>
>  ----------
>  Tom Rawson
>
>
>
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