An area for operations growth - Storage Area Nets in MANS

Rubens Kuhl Jr. rkjnanog at
Mon May 19 11:36:34 UTC 2003

Non-flawless software (i.e., 100% of it) is usually dealt with storage
snapshots; if they are kept local or remote, that's a design choice that a
metro SAN can impact.

Doing backup/restores thru a metro SAN also has some advantages on
facilities with tight-controlled physical access; the bandwagon that moves
tapes to off-site storage still has more bandwidth than the fiber, but it
can also be used to smuggle <insert-your-favorite-paranoia-here>.


----- Original Message ----- 
From: "Petri Helenius" <pete at>
To: "Gordon Cook" <cook at>
Cc: <Nanog at>
Sent: Monday, May 19, 2003 7:33 AM
Subject: Re: An area for operations growth - Storage Area Nets in MANS

| 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.
| Pete
| 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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