[plug] RAID Setup

[Craig Foster]

> -----Original Message-----
> From: plug-bounces at plug.org.au [mailto:plug-bounces at plug.org.au] On
> Behalf Of Phillip Bennett
> Sent: Tuesday, 8 April 2008 7:49 PM
> To: plug at plug.org.au
> Subject: [plug] RAID Setup
> 
> Hi everyone,
> 
> I'm looking into building a RAID setup for our new Virtual Machine
> host.
> I'm trying to condense around 4 or so servers into one box with Xen,
> using
> ATA over Ethernet as the storage solution.
> 
> I've found a great case and setup to use (via http://xenaoe.org) that
> houses
> 15 drives.  I can fill it up for very little cost, but then I'm
> wondering
> what kind of RAID to use...  We don't have huge space demands and I'm
> sure
> anything will be faster than our current storage solution.  However, I
> *would* like some decent speed and redundancy.
> 
> So: How would you set something like this up?  RAID5, or maybe some
> groups
> of RAID0+1 or RAID 1+0?  What would give me the best speed as well as
> resiliancy?

RAID5+1 is our current choice for both speed and resiliency.
Software RAID5 on hardware mirrored Initio or 3Ware SATA RAID
controllers (with a hot spare on each controller).

R5 in case a controller fails, and put the R1 on hardware (not that crap
firmware) so mirroring is handled by accelerated/ dedicated processors. 

RAID5 by controllers means adding more space is simply add 2xHDD + 1xHS
HDD + 1xR1Controller and expand the volume over the new "drive".

Hot spares are a good choice as failures never seem to be nice enough to
wait until a good time :P

I'm still open to suggestions on better options on RAID controllers as
3ware is expensive, initio isn't normally carried by every computer
wholesaler, and Adaptec (rings bells with PHBs) are crap at the moment. 

> I was thinking of starting with 15 disks, using two for hot spares,
> leaving
> 13 disks between 2 RAID sets - one of 8 and one of 5 disks.  The
> smaller set
> would be RAID5 and used to host the virtual machine images and some
> less
> used files (PC images, drivers etc..) and the larger set would be for
> our
> company data.  I'm just at a loss for how to do it best.  At the price
> I can
> get the parts, I was actually thinking of mirroring the 15 disk
> enclosure
> entirely (ie Software RAID1) to shut the boss up about a single point
> of
> failure.

Remember mirror across multiple resources, meaning put in a NIC and
either a dedicated switch or crossover cable for each mirrored AoE
enclosure. NICs and switches die as well.:P

> 
> Does anyone see any problems with this or have any suggestions?
> 
> Thanks in advance,
> Phil.
> 

CraigF.