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ZeroNines Press Coverage
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How Zero Nines Ensures Uptime
By Audrey Rasmussen - Enterprise Management Associates
April 23, 2003
Many management products kick in after a problem occurs,
requiring some lag time before users can resume their work. In
some cases, it could take minutes, but sometimes data recovery
could take days. Can your company have an application that's
down for days? Obviously, it depends on the application, but for
mission-critical applications, there can be serious impacts on
the business.
I recently became acquainted with a product from Zero Nines that
can help IT to avoid downtime altogether, rather than reacting
once it happens. It's particularly useful for applications that
can't go down or can tolerate only a minimal amount of downtime.
Here's how it works. Zero Nines uses a specially designed switch
that takes user application requests and multicasts them to
several application servers, creating multiple application
streams running in parallel. Zero Nines bases its
recommendations on statistical analysis that shows that
multicasting to three servers enables ultrahigh availability,
and multicasting to two servers provides five nines (99.999%) of
availability.
Each of the receiving application servers thinks it is the
primary server processing the request. If one of the servers
goes down in the middle of processing the transaction, one of
the other servers takes over immediately, with no lag time
perceived by the user. All of this happens without the user
knowing that the application server has gone down, because the
application is still running just like it's supposed to. Zero
Nines handles the processing sequences to ensure that the
transactions are handled in the correct order.
In addition, once the server is online again, it automatically
"catches up" with the processing that it missed during the
outage, so that it's up to date. Failover is not necessary
because the application is running in three places, in real
time. If a server goes down, there are two other servers that
can still service the user.
An application can always be available, assuming that all three
servers running it are not disabled at once. If your sites are
carefully planned, statistically, the likelihood that all three
sites are rendered inoperable simultaneously is extremely small.
The application servers can reside within the corporate network
in disparate locations, or companies can take advantage of Zero
Nines' partnership with AT&T, which offers the capability to
leverage external telecommunications infrastructure for added
resiliency.
Interestingly, Zero Nines can handle most platforms for the
target systems, including older operating systems like Windows
98. It can handle heterogeneous target systems, heterogeneous
both in hardware and in operating system. So companies can
leverage the equipment that they already own, old and new,
rather than having to buy identical systems, as some
high-availability products require.
What makes this product different from others is that it aims to
provide business continuity at the application level. Others
focus on redundancy or recovery at the hardware level or at the
data level. And some products focus on what can be done once a
problem occurs. However, Zero Nines' focus is to keep an
application running, where the infrastructure is resilient
enough to continue delivering the application service, despite
specific problems in the infrastructure.
During a demonstration of the technology, and unlike most
demonstrations, the Zero Nines people invited me to pull out any
cables and try to break it. To borrow a phrase from old Timex
commercials, "It takes a licking but keeps on ticking." Zero
Nines is an interesting product for applications that need high
availability.
Copyright Network World, Inc., 2003
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