More about CMNT's SAN over IP, the underlying technology of EMC's SRDF over IP......
From an EMC webchat:
12:18:21 2000 atlunch {question presented} What does DWDM have to do with storage?
12:18:41 2000 jim_rothnie {public msg} DWDM (dense wave-division multiplexing) provides a cost-effective way to extend a SAN (and almost any other kind of network) by sharing strands of dark fiber among many applications. For example, in NYC many financial services companies are using DWDM to implement our remote mirroring product (SRDF) across the Hudson River to disaster recovery sites in NJ. DWDM makes this kind of implementation highly cost effective.
12:39:53 2000 mab {question presented} When do you see optical networking taking off. There is a lot of talk about "dark fiber," when will it be lit?
12:40:13 2000 jim_rothnie {public msg} It's taking off today. There is a huge amount of DWDM and related equipment being installed in 2000. Applications that will consume all that dark fiber are coming on line every day. For us the exciting thing is that consuming the dark fiber implies consuming storage because it's all about access to information.
12:41:32 2000 emcatnplusi {question presented} How far can a disaster recovery site be from the production site using SRDF?
12:41:52 2000 jim_rothnie {public msg} The two sites can be hundreds of miles apart. There are thousands of customers around the world using SRDF for disaster recovery with distances ranging from campuses (a mile or so) up to hundreds. Customers also use SRDF to replicate databases over thousands of miles.
Message 14470543
If you are already utilizing remote mirroring
over dedicated lines, switching to IP may give
you, by rough estimates, the potential to cut
your tariff costs in half. In addition, the
change simplifies the variety of networks that
you have to manage. Unused IP capacity can be
utilized elsewhere within the enterprise. If
you are not making remote copies because of
the apparent high cost and inherent
complexity of T-1, T-3 and ATM lines and
controllers, the cost of entry now has been
lowered significantly. With SRDF over IP, many
large enterprises can more affordably protect
all of their enterprise’s mission-critical
data from local failures.
You may think that you are adequately
protected currently, and you might be. SRDF
and similar remote copy facilities from other
storage vendors have been around the mainframe
world for more than five years. However, with
more and more mission-critical application
running on UNIX and NT servers, you may have
just scratched the surface in providing
adequate protection for your enterprise. While
SRDF has been running on open servers for three
years, many enterprises have not taken advantage
because the available telecommunications methods
were deemed too costly or inappropriate. EMC
listened to its customers and now offers SRDF
running over IP. In doing so, EMC also offers
other solutions for its Symmetrix customers.....
Changing Economics
The large percentage of enterprises that have
chosen not to do extended-distance mirroring do
so because the implementation cost is perceived
to be far greater than the probabilistic cost
of failure. But during the last five years,
customers and partners have become less patient
with delay and more exacting in their
information and processing requirements, be
they specs or delivery dates. Along the way,
the time-value of information has significantly
increased. Earlier, different scenarios were
discussed, showing different impacts of failure
and varying needs for timely recovery. These are
still hard to quantify, but most executives
readily accept that the time-value has
dramatically increased. Equally important to the
return-on-investment analysis is the falling cost
of doing extended-distance mirroring.
To get a sense of the changing cost parameters,
The Clipper Group interviewed a senior network
manager with a major telecommunications firm.
The firm has been using SRDF with mainframes
over an extended distance for a number of years
using long-distance lines and the necessary
controllers. They had determined long ago that
they could not afford to be without the data on
the mainframes; but they were always looking
for ways to do it more efficiently. The firm
is now a beta test site for SRDF using IP. The
network manager declared that "using IP for telecommunications [at tariff rates] would
generate [a savings of] at least half of the
cost." Because they already have high-capacity
and high-performance IP bandwidth installed,
the potential savings are even greater. He
said: “The IP network goes everywhere. With
SRDF over IP, we can do DASD mirroring from
anywhere to anywhere in the company." With the
cost reduced by half, he predicted that after
going into production with mainframe data
being mirrored over IP, the firm would
"expand the SRDF over IP solution to mid-range
platforms [UNIX and NT]."
Clearly, the need (and benefit) already exists
to mirror (and copy) additional data over
extended distances. The ability to do it over
IP at a perceived "reasonable cost" led to the
decision to go forward with extended-distance
mirroring for open systems via SRDF over IP.
The manager’s beta test experience led him
to conclude that there is "absolutely no
reason not to expect to match existing
performance [over telecomm lines] with IP."
In fact he "expects better performance
[with SRDF over IP], overall, in spite of
more hops, because our [high-capacity]
routers are more efficient." For most
enterprises, this level of performance may
not be achievable without significantly
enhancing their existing IP infra-structure
to meet real-time delivery requirements. To
ensure that the response time and quality of
service meet your requirements, The Clipper
Group recommends that you carefully select
the remote copies/transfers that you want to
deploy over private IP networks. With
dramatic savings on telecom costs, extended-
distance mirroring via SRDF over IP might be
more clearly justified on a cost basis alone.
Other enterprises might not have the IP
infrastructure of a telecommunications firm,
but they, too, have IP networks and SRDF over
IP could deliver substantial benefits.
Extended Distance Copying and More
Rapid recovery is not the only reason to
implement extended-distance mirroring. Copies
of files or subsets of databases can be
distributed to remote arrays, facilitating
local processing. Consider an Internet
retailer that has a browse-to-buy-ratio of
20:1. Most of the hits to the web site are
browses and speed is of the essence. Why not
have two copies of their browsable web pages,
say one on the East Coast and the other on
the West Coast? Access time would be improved,
because the average distance and number of
hops between the user and the web page have
been reduced. Of course, the underlying
inventory database would have to reside at a
single location, which would be automatically
mirrored by SRDF over IP to the opposite coast.
This also can be valuable in feeding a data
warehouse, consolidating databases, backing up
email files, or just moving data between
systems, all without server involvement.
While the currency of data is important, it
often may be acceptable to operate in a semi-
synchronous or asynchronous mode, effectively
allowing the source database to continue
processing without waiting for the remote
copy to catch up.
Once you have SRDF over IP, the data on
one Symmetrix can be moved to any other
Symmetrix on your private IP network,
regardless of distance and with less regard
for the time it takes to get to its
destination. With extended-distance
synchronization, data centers across a
geographically-dispersed network can have
copies of the latest backup files, each
ready to go in case of a primary system
failure, while heterogeneous servers can have
equal access to data for data marts and
warehouses. Remember that it’s all about
timely access to valuable data. More long-
distance copying will be a significant added
benefit in the extended-distance ROI equation.
For some, it will be sufficient justification by itself.........
New Possibilities with IP-based SRDF -- EMC listens to its customers
The Clipper Group
February 11, 2000
emc.com |
