[Bassetlug mailing] Setting up RAID

[Danny Roberts]

We initially tried using the software RAID (via the Ubuntu 
Installer/Partitioner) but it seemed incapable of creating the RAID 10 
setup we wanted so Philip switched it over to hardware RAID.

RAID 5 is great (we use a lot of it at work albeit on that "other OS") but 
that would lack the improved performance Philip wanted from the RAID 10 
configuration.

I think playing around with RAID and finishing off Philip's web server 
could be great for the next LUG meeting, I know I'm certainly interested 
in learning more. And of course if no one else wants the Compaq servers 
etc I'd love to give them a new home ;-)

Mark do you have any experience in setting up complex/esoteric RAID setups 
like RAID 50, RAID 60 or even RAID 100? That would probably be beyond the 
scope of one of our meetings but I've done a lot of reading up on RAID 
today and its whetted my appetite.

Kind Regards

DANNY ROBERTS
EMEA Cross Platform Services - Evergreen
CSC

GOS   I    p : +(44) 1246 523181    I    droberts23 at csc.com    I 
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Rev Mark Pengelly <minister at thecrossing.co.uk> 
Sent by: bassetlug-bounces at mailman.lug.org.uk
19/03/2009 15:44
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Re: [Bassetlug mailing] Setting up RAID






Was Philip's discussion all relating to mdadm? We use that on the
crossings' server. it is of course 'software raid' not to be confused
with a hardware raid controller.

Occasionally we have had glitches with our raid 1 setup, ie a disk drops
out of the raid and then md commands are used to add it back in. So far
it has always done so, although sometimes we have had to do a cold
reboot of the machine.

Hardware raid is preferable if available. Most compaq servers raid
hardware is supported in linux and can usually see a partition as a boot
device when installing, once the array is setup using the proprietary
software (SmartStart in the case of compaq).

I have a pci hardware raid card on my main ubuntu machine, but never
really got it working properly.

Many modern motherboards with sata raid are actually only using
(windows) software to create the raid, it's not full proper hardware
raid (I think).

if anyone wants to play with raid I have 2 x compaq 1500 servers, one
with 5 drives, one with 3 drives in it. I had redhat 6 running merrily
on it about 5 years ago, I also have a scsi attached array case with
another 7 drives in (only 2.1gb per drive). I've been meaning to clear
this out for months, free to a good home! only catch - you need to have
ear defenders on when all the drives start up! i ran mine in the
garage!! Perhaps I'll bring it to bassetLUG show how to set it up and
then someone else could take it home!?

Sounds good Philip, sorry I missed it! Raid is definately cool, what
about raid 5?! my favourite!

Mark



On Thu, 2009-03-19 at 13:55 +0000, MJ.Wells wrote:

> Good to see 'old' and 'new' members at the meeting last evening where 
Philip
> gave us a very informative demonstration of setting up RAID in Ubuntu.
> 
> Philip told us that he had occasionally seen problems when he set up 
some
> systems which he felt were due to not having identical drives in the 
array
> as is recommended. 
> 
> Philip then showed us that  setting up the RAID in the BIOS causes Linux 
to
> be unable to find the boot loader so that the most expensive of 
equipment
> just loops at boot as it could save me much time in the future. It seems
> that the boot partition has to be excluded from RAID.
> 
> Philip went on to explain the difference between RAID 0 (striped) and 
RAID 1
> (mirrored) along with the more complex RAID 10 (1+0) which combines 
both.
> After a detailed setup of the partitions using the hardware RAID which 
led
> to the failure to boot, Philip showed us the process of setting up the
> drives in the Ubuntu Server install. Finally we looked at leaving the 
setup
> of the RAID until Ubuntu had been fully loaded on some of the disks.
> 
> Unfortunately, even though we extended our evening until well past 10pm 
as
> we were enjoying the demonstration so much, we had to leave the full use 
of
> mdadm until another time.
> 
> I have not encountered this technology before and have learned a lot. 
Thanks
> Philip for a very informative and useful demonstration. Now ... I wonder
> where can I lay my hands on four unwanted 500Gb-ish drives so that I can 
try
> it all for myself?
> 
> Martin
> 
> 
> 
> 
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> Bassetlug at mailman.lug.org.uk
> https://mailman.lug.org.uk/mailman/listinfo/bassetlug
> 
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