From: P T (pt_lbIZZAThotmail.com)
Date: Mon Apr 05 2004 - 11:09:36 EDT
Firstly, the objective of this paper was to get information out. I'm not
selling anything, or competing with any of these products. If customers are
informed of these caveats/tradeoffs, and still decide to purchase a pair of
GSLB devices for $60K, great! Then the objective of this paper would be met.
The customer would have made an informed decision. Problem is, in most cases
customers are being told they can use multiple A records and simultaneously
have "control" (as you put it), and/or are not being told about the browser
caching issue. I'm guilty of personally telling customers this, many who
listen on this list. (Again, sorry about that, I didn't know!).
Secondly, after speaking with hundreds of customers about SLB/GSLB over the
years, I can't think of a single customer that is both in the market for a
multi-site H/A (or "business continuity") solution, and is also OK with
potentially every user having to restart their browser or reboot their
computer upon a site, Internet connection, power, or SLB-pair, failure -
especially a high-end customer that would be able to afford such a device.
Users just don't think "hey, the problem is probably my browser". Clearly
single sign-on is lost if the server/site blows up (that's in the paper).
For most sites, that session loss happens even if a single server in a farm
fails (not even considering multi-site). In that case the user is prompted
to log on again, and can recover transactions from a shared database.
Unfortunately, there's no practical way to prompt a user to restart their
browser, so without multiple A records, for all such users (maybe all
users), the entire global site appears to be off the Internet.
Thirdly, multiple A records were in use well before Alteon or Cisco or F5 or
RadWare had GSLB products, and many marquee sites use multiple A records
(for both multi-site and multi-homed single site), so although what you say
about "some browsers" is probably technically correct, I think it may
obfuscate the point in this context - that multiple A records are a
fundamentally sound and well tested approach.
Fourthly, the "control" that can actually be achieved with a DNS based GSLB
device is way overrated (even ignoring the H/A issue). I purposely avoided
that topic in this paper, primarily because most GSLB customers these days
just want active/backup ("business continuity"), don't have a site in
Zimbabwe, and could care less about proximity/load/etc., but also because
it's a different subject altogether - maybe a good reason to do a "Why DNS
Based GSLB Doesn't Work - Part II".
(score - 2 people guessed Tasmanian Devil, nobody guessed Bing)
>From: Jesper Sørensen <jesIZZATmaerskdata.dk>
>Subject: Re: [load balancing] The GSLB Page of Shame
>Date: Mon, 5 Apr 2004 09:52:16 +0200
>I've been following the discussion, and I feel the urge to jump into it :D
>Let's assume that the application is statefull.
>What happens in a multi a-record setup, when a single site has a disaster?
>- Well any user currently
>connected to that site, will have to relogon and everything they did is
>Let's assume we have some backend replication, so that in case of a site
>disaster the user is able
>to connect to a different site without having to relogon.
>Site fails, user donâ€™t even know it.
>Letâ€™s do the same with a GLSB setup.
>Site fails; user has to restart browser. And then relogon and redo what he
>/ she was doing.
>So why would anyone do GSLB? Simply put: Control
>Who needs control? Or why would anyone need that kind of control?
>Well the Internet spans the World, and in many countries, especially
>emerging economies, the
>connections to the rest of the world are painfully slow. If these countries
>are important to you,
>then you need control. If not then go with a multi a-record setup, and live
>happily ever after (with
>a bit of luck)
>One last thing, multi a-records arenâ€™t all that good - Some browsers will
>simultaneously to two or more of the IPâ€™s returned.
>MÃ¦rsk Data A/S
>Tlf : + 45 39 11 22 37
>Fax : + 45 39 11 27 45
>Cell : + 45 29 49 54 90
>MCS : CPHMDATA,COM
> "P T"
> <pt_lbIZZAThotmail.c To: lb-lIZZATvegan.net
> om> cc:
> Sent by: Subject: Re: [load balancing] The
>GSLB Page of Shame
> 05-04-2004 01:30
> Please respond
> to lb-l
>BGP convergence doesn't GSLB happen quick enough to avoid connection
>failure, and therefore cannot replace multiple A records for H/A. That's
>most customers use multiple A records. Problem is, multiple A records break
>GSLB, and most customers (or vendors) don't know that.
> >>It's obvious that GSLB works or vendors wouldn't be selling it,
>Vendors are making claims that are technically incorrect, exactly specific
>to this issue. The claims are on their Web sites, in their manuals, in
>sales pitches, etc. You are saying all this is well known, but you are
>wrong. Look for yourself.
> >From: William Bivens <wjbivensIZZATdigitalme.com>
> >Reply-To: lb-lIZZATvegan.net
> >To: lb-lIZZATvegan.net
> >Subject: Re: [load balancing] The GSLB Page of Shame
> >Date: Sun, 4 Apr 2004 15:56:07 -0400
> >First off, let me state quite simply that my response has nothing to do
> >with my current employment, however I'm (NetScaler) on the side of the
> >right in that NetScaler doesn't charge for the functionality that you
> >As a vendor system engineer my first statement is that in your examples
> >a catastrophic event (Internet connection, power, switching, and/or
> >load balancing failures) without a doubt anyone would be best served
> >BGP4 for high availability.
> >Now let me back track a little so you can get a better understanding on
> >position. First, the feature/product is called Global Server Load
> >Balancing (GSLB) not Global Site High Availability. Pointing to GSLB as
> >failed HA solution for catastrophic failures is equal to saying that SLB
> >(Server Load Balancing) is a complete failure due to a site Database
> >failure. So I feel that in general your document has very valid points
> >the High Availability aspects of GSLB however I'm a firm believer that
> >should be combined with BGP4 for any sensitive transactional environment
> >where time equals lots of money and I would bet that any
> >ReallyBigWellTrustedFinancialSite's have probably rolled out an EBGP
> >routed environment before doing a GSLB installation.
> >The problem is that your document assumes that the "overwhelmingly most
> >compelling reason that Internet sites are hosted in multiple locations
> >high availability". However there are several reasons that companies
> >choose GSLB: even load distribution across multiple links, risk
> >mitigation to spread Internet load across multiple POPs, site
> >(through planned fail-over), reduce data center costs (colocation
> >competition), site/application scalability, and of course site high
> >availability to name the majority of reasons but in general I wouldn't
> >call it the most compelling reason.
> >The reality is most sites/companies/customers don't perform real time
> >synchronization (assuming the application requires it) between
> >geographically dispersed data centers without a BGP4 implementation. In
> >the last 3 GSLB conversations I've had customers are asking that GSLB
> >provide automatic site fail-over and the majority of reasons stated is
> >to the fact that Database work (primarily sycronization) needs to be
> >completed before bringing up the cold site online. Anyone who's been
> >quoted an EMC SRDF solution and the bandwidth requirements (especially
> >across the country/globe) will probably know that real time data
> >synchronization in addition to automagic site fail-over on catastrophic
> >failure is the design goal, but often times is more costly then the
> >application revenue generation during the 30 minute black out of the
> >existing IE customers with a DNS cache.
> >Now for the business side. Your document states that it's "the
> >responsibility of the manufacturer, not the customer, to determine if a
> >product adds value remotely close to what is represented in marketing
> >claims." Now in general I believe that in all cases marketing claims
> >should be responsible, however, to think that "customers" should not be
> >responsible for making vendor product selection when the sole purpose of
> >the IT/Technical Operations personnel who are being paid by the company
> >provide technical solutions to business problems is a completely
> >irresponsible statement on your part, a manufacture cannot know every
> >business requirement that will be needed for the entire market that they
> >service. If the people that are hired by a company don't take the time
> >do due diligence to evaluate, speak with "like" customer references, and
> >have business discussions with Vendor account executives they (customer)
> >should be liable for not doing their job. And if the vendor can't
> >an evaluation or customer references then customer should move on but I
> >can't feel responsible for people who make technical decisions off a
> >marketing product feature list.
> >So for a little constructive criticism on your document, like I've
> >previously the technical details are pretty tight in general but seem to
> >be bias and during my reading I called it a manifesto. Either way it
> >comes across as a sort of personal vendetta or a technical sales pitch
> >which isn't objective. The biggest problem overall is the there seems
> >be no continuity between the initial claim that no "DNS based GSLB
> >solution can function properly...to also provide high availability"
> >probably should be sidenoted/caveated with "during a catastrophic
> >failure") and it continues to expand and try to address topics such as:
> >Proximity based GSLB on the Internet
> >Multiple A records for HA (but at the same time doesn't work for a
> >Active-Standby sites)
> >HTTP Redirects (which works fine, except someone COULD bookmark)
> >GSLB Advertisement Flapping
> >IP proxy
> >Backup redirection
> >Now it's perfectly fine to discuss other topics, the problem is that
> >of these solutions weren't designed to address the catastrophic failures
> >that were mentioned in your document so it's entirely unfair to pull out
> >the almighty trump-card of "it doesn't work in a catastrophic failure"
> >in the case of GSLB Advertisement Flapping by changing the game to talk
> >about outages outside of catastrophic to discredit GSLB health checking.
> >It's obvious that GSLB works or vendors wouldn't be selling it, or more
> >importantly, companies wouldn't be buying it. The old adage, if you're
> >not part of the solution your a part of the problem definitely applies
> >this document. I'd love to see it updated as an informative document
> >shows both sides and tries to propose solutions to a particular
> >but in its current state of "I'm going to pee on all the cheerio's by
> >dragging them into unrelated discussions" although informative is not
> >helpful in general.
> >Jay Bivens
> >NetScaler, Inc.
> >System Engineer
> >On Apr 1, 2004, at 7:04 AM, P T wrote:
> >>Jay, that's just it... there are _no_ workarounds that fix the issues!
> >>thought the paper did a pretty thorough job of explaining why the state
> >>of the art workarounds are not sufficient. Did you read it?
> >>It's not like any one piece of this information is new, but the sum
> >>of it is definitely not widely known within SLB vendors. For example,
> >>several of them, including the current market share leader, have
> >>information on their Web sites explaining how they return DNS A records
> >>in a list with the "best" IP address first. That doesn't work on the
> >>Internet! The DNS gurus laugh in our faces. (Hey, I didn't know it
> >>either, how embarrassing!). It's OK to be wrong. As technologists we
> >>learn from mistakes, fix the stuff we build, sell stuff that works,
> >>right? So GSLB doesn't work as we all had hoped, and we can't fix it.
> >>There's no sense pointing fingers or lamenting about how browser
> >>should change to observe TTLs or SRV records or whatever... even if
> >>fixes were released in software today we would have to live with the
> >>installed client base for years. Now we know that, and move on. I hope
> >>your company, NetScaler, takes such higher ground.
> >>What would really be shameful is for vendors to, after realizing issues
> >>such as these, continue promoting features and products that do not
> >>as advertised.
> >>>From: William Bivens <wjbivensIZZATdigitalme.com>
> >>>Reply-To: lb-lIZZATvegan.net
> >>>To: lb-lIZZATvegan.net
> >>>Subject: Re: [load balancing] The GSLB Page of Shame
> >>>Date: Wed, 31 Mar 2004 19:38:08 -0500
> >>>It's a shame the GSLB manifesto couldn't be more neutral, it makes
> >>>very valid point. There are several reasons to use GSLB and several
> >>>workarounds for the specific problems, it just seems that the author
> >>>chose not to highlight or know them.
> >>>Jay Bivens
> >>>On Mar 30, 2004, at 2:01 PM, P wrote:
> >>>>A paper that describes why DNS based GSLB solutions cannot work
> >>>>reliably for browser based clients.
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