An area for operations growth - Storage Area Nets in MANS

Petri Helenius pete at
Mon May 19 10:33:01 UTC 2003

Although I agree that storage networking as a backup/tandem resiliency 
operation makes a lot of sense,
it does not come anywhere nearly "free" because the assumptions made 
there require flawless software.
If you always synchronize your systems you'll also blow them both out 
when you hit a software issue
and as most of the audience is painfully aware, they are not infrequent 
enough to count out of the equation.

So you need to keep track how to re-synchornize  after an 
upgrade/failure/etc.  With a large stream of
updated data on the system keeping the state difference becomes 
expensive quickly. (unless you are going
to re-sync everything after a failure, and then you'll be vulnerable 
until that's completed)

Pointers to perfect SAN solutions appreciated.


Gordon Cook wrote:

> Roxane Googin  is usually ahead of the competition in spotting trends 
> in data net use.  here is what has has to say about enterprise use of 
> MANs.
> COOK Report:  Where are the metro area networks going?
> Googin:  Probably the killer application for the MAN is grid computing 
> and storage area networks.  A lot of people think the driver for 
> broadband access to the home is going to be multi-media. People, when 
> they think about next generation networks, think home use.  But this 
> is never where the money has been.  And no phone company is ever going 
> to build the infrastructure.
> Although these new real time applica tions will clearly send more data 
> over the network, the real killer application is going to be remote 
> storage and synchronous storage.  Synchronous storage means that you 
> have two large servers doing the exact same thing at the exact same 
> time in two different locations.
> COOK Report:  Like a decentralized disk array?
> Googin:  Yes.  The backbone has to be incredibly fast because you 
> cannot complete a transaction until you have acknowledgments from both 
> disk drives.  This will happen.  Probably this year.  What they are 
> already doing is taking fiber channel and putting that on a Cienna 
> Core Director optical switch port.  Half of the ports being sold on 
> the Core Director now are fiber channel.  They aren't even Ethernet.  
> And this is used for storage area nets (SANs).  These are corporate 
> MANs and will have nothing to do with sales to service providers.  
> They are bypass business services where the storage arrays may not be 
> more than a kilometer or two apart.  These SANs are backing up 
> continuously terabytes of data.  We are talking huge applications that 
> will use every bit of access to every bit of capacity they can get.
> COOK Report:  Is 9/11 a motivation for this?
> Googin:  Partly. Not only that but the whole paradigm of the real time 
> organization will drive it.  It used to be that your server had its 
> own storage.  It was a "stove pipe" connected to the CPU.  Now as soon 
> as you decouple that "stove pipe," you can put it anywhere. What they 
> are finding is that if they have two of them that are mirrored in real 
> time and place remotely that they do not have to do as much management 
> of resources.
> COOK Report:  Then forget the disaster back up and recovery 
> operations?  Those are the next to be marked for extinction?
> Googin:  Oh yes.  It is so elegant.  The new architecture cannot be 
> supported on direct attached storage.  It must move off the server and 
> it is doing so.  If you have to go through a server to get to the 
> storage, it simply doesn't work.  Storage can't become just a utility 
> until you move it off the server.  The MAN will be backing up 
> terabytes of data regularly and in real time. Disaster recovery, in 
> real time, comes for "free".
> For more detail please see
> Fiber & Wireless as First Mile Technology - Fiber Business Models & 
> Architecture

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