[Beowulf] RE: Storage - the end of RAID?

Bill Rankin Bill.Rankin at sas.com
Mon Nov 1 11:21:36 EDT 2010


> Um, it's not really RAID 1 when the drives are in different servers.
> Although there's not much point in arguing about that.
> 
> -- greg

My knee-jerk reaction to Greg's statement was going to be something snotty and along the lines of "what part of 'R' don't you understand?" ;-)  But upon further pondering and also going back and re-reading the original article a little more slowly, I think that there is a point in there.

Now, one thing I do have an issue with is the article's title claim that RAID is somehow dead.  This is clarified in the very first sentence where he identifies that this refers to "costly RAID controllers".  Terribly misleading but as someone mentioned earlier it does grab your attention.

But in a sense this is old news to us.

What the article essentially addresses is that with the huge increase in the I/O capability of other pieces of the system (CPUs, busses, etc) the model of having all your data accessed by going out on the wire and pulling it in from some remote (possibly multiple) high end storage servers cannot survive.  At least not for "active" data.  

Well, duh.  Personally I've been using clusters to crush some decent high-end storage arrays since around 2003.  Back then the general rule was that we had local disk on the nodes and you would do any significant I/O to those disks.  We would stage static copies of input data (eg. Genomics databases) to those disks also just to avoid going out on the wire.  

So we threw out RAID years ago for our active data.  Where we did keep it was for our less active data - home directories, executables, etc - where we did have a need for a definitive, coherent storage image and availability was more important that absolute performance.  But this too is starting to change as the node count rises.

I think that the current thinking is that while disks have gotten very large, their I/O performance has not kept pace.  With the cost of solid state storage coming down in price now, it makes a lot of sense to start replacing disks where we have single point bottlenecks in our I/O chain.

So I look at the whole discussion as the realization that finally the rest of the world is catching up to us.

:-)

-bill




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