Linux Hardware RAID Configuration

[Mike Garfias]

Jeff -

I'll be happy to help a lot more once I'm back in town.  (Tuesday will
probably be the soonest).

Until then a few things:

I did a lot of research trying to build a server last dec that had "hardware"
raid.  The result: If it doesn't say 3ware on the card, I'm 99% sure its a
software raid setup.  These things don't really do raid in hw, they do it in
software through drivers - they actually work on windows, but I still wouldn't
do this.

Even though my expensive tyan dual opteron board hard onboard "hardware" raid,
I still ended up doing software raid as it was a) supported b) easier to
setup.

For the record, I've done lots of real HW raid, and as was said before, the OS
will see only one drive.  Even without the drivers, the OS will see one drive
(provided you have one raid set built).

What I ended up doing was: three sata drives, two mirrored, one hotspare.  I
created two slices on each disk, done for the root slice, and one for the LVM
slice.  Then build the soft raid config.  Then used LVM to further divide up
the 2nd slide into my various file systems.

It was a pain in the butt, and I'll never do soft raid again - but, a 3ware
card was $2-300 over the budget at this time.  Next time I budget a bit more.

Also, I ended up running ubuntu on this thing.  Advice: make sure you run a
2.6 kernel, the 2.4s blew up (deb + ubuntu).  Also, the 64bit deb port is 1/2
baked at this time.

You could always try Solaris x86 :)

Jeff Garland spoke forth with the blessed manuscript:
> Darrin Chandler wrote:
> 
> >If it's *really* hardware raid then you'd only see 1 disk. You can only 
> >see the disk at all through the controller, after all. So the controller 
> >isn't taking over at that level. 
> 
> This is my suspicion...and what you are saying validates what it says in:
> 
> http://www.linuxhomenetworking.com/linux-adv/raid.htm#_Toc92809999
> 
>   Hardware RAID configuration is usually done via the system BIOS
>   when the server boots up, and once configured, it is absolutely
>   transparent to Linux. Unlike software RAID, hardware RAID requires
>   entire disks to be dedicated to the purpose and when combined with
>   the fact that it usually requires faster SCSI hard disks and an
>   additional controller card, it tends to be expensive.
> 
> So I'll goof around with the bios settings a bit to make sure I have 
> them right.
> 
> >You may have one of the SATA 
> >hardware/software combo raid systems that have been going around (I have 
> >one). If your OS doesn't support it then you can't use it as raid. I'm
> >not at all sure of Ubuntu. 
> 
> The system doesn't have an OS yet.  I've been experimenting with a few 
> distros as I'm ready to give up on Mandrake that I'm using for eons and 
> try something else.  So far it's been mostly problems.  The straight 
> Debian 3.1 R1 hangs on the install, Ubuntu 64 bit Live CD (acquired as a 
> prize at the Dev meeting the other night, Thx!) blows up on the X 
> startup.  So I was trying the Ubuntu 64 bit installed CD to see if I 
> could work out an X config.  I've long since passed my usual tolerance 
> for this sort of 'fun'....but I digress...
> 
> As for the RAID support, Ubuntu clearly has it, but I think what they 
> are talking about is Software RAID where the hardware isn't used.
> 
> >I know there are drivers and stuff for it for 
> >Linux, but I don't have any details. I believe the guys at Linux 
> >Certified will ship that way as an option. Wish I had more to tell you.
> 
> Thx -- every little bit helps.
> 
> Jeff
> 
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