Run some tests and find out if you disks are a bottle neck or not.  If you start finding out disk performance is holding bask your design, then upgrade to SCSI.  I am betting that the network is going to be the bottle neck though.  

RAID 5 is awsome.  It gives you parity and if one drive fails you don't loose everything, like you do with raid 0.  RAID 10 is very good, you can get any performance benefits of RAID 0, but if the array fails you have a back-up copy.  really good way to go if you can afford the downtime for bringing up the back-up.  That is teh most important thing with RAID, learn to do you restores and bring back-up systems online!!!!!!!

-------RAID Overview for newbies----------
RAID 0 - mirroring. basically it makes an exact replica of one disk on another disk

RAID 1 - stripping. it uses two or more disks and spreads the information across them (i.e. first bit goes on the first disk, second bit goes on the second disk, third bit goes on the first disk....)

RAID 2,3,4 - hardly ever used

RAID 5 - striping with parity.  uses three or more disks and spreads the data across them using one for parity.  Similar to RAID 1 but on the third disk it would add bit 1 + bit 2 and put the answer on disk three.  that way if disk two fails you can replace it the RAID will rebuild disk two by subtracting the bit on disk three from the bit on disk one.

RAID 10 or 0+1 - this uses two stripe sets. One is a mirror of the other.

RAID 50 or 0+5 - This is for really ANAL people (I always use this in production enviorment where I can't loose data).  uses two raid 5 disk arrays.  one is a mirror of the other.

this is very generalized and not exacltly how raid works, but gives the good idea.

---------------------------done----------------------



----------------------------------------------------
> > Are you sure the cost savings over SCSI RAID are _really_ there?  How much
> > mass storage do you need?  I bought 15 18GB U160 scsi drives on ebay for
> > $130ea and then got a 64bit PCI AMI MegaRAID Elite 1600 for $350.  The
> nice
> 
> How often can you find that kind of great deal?  We can't survive off of
> Ebay for a steady stream of parts, when we need to make many of these
> systems.  Also we probably can't buy parts on Ebay with the DOE's bid and
> procurement laws.
> 
> I suppose I should look at SCSI choices...
> 
> > RAID 5 does nothing to improve performance.  It has to do a parity
> > calculation and there is some overhead in this.  SCSI RAID off loads this
> > to the RAID controller CPU.  I would think the cache on the controller
> > would probably offset this loss.  The memory interleaving of the AMI
> > controllers would probably go even further to offsetting that.  One last
> > benefit of the SCSI solution is the MegaRAID driver is very well developed
> > in linux.
> >
> 
> Maybe I'm completely wrong about RAID 5.  Anyway, I'm going to try it.
> Anyone have anything against RAID 0 + 1?
> 
> 
> ---
> You are currently subscribed to luau as: dusty@sandust.com
> To unsubscribe send a blank email to $subst('Email.Unsub')