Why not NT clusters? Need arguments.
Schilling, Richard
RSchilling at affiliatedhealth.org
Mon Oct 9 08:02:29 PDT 2000
O.K. Let's try this again . . . let me rephrase my original message so that
I don't get misunderstood:
NT sucks as a platform upon which to build distributed processing
architectures such as a beowulf class machine. It's nice to see some strong
data to support that because convincing people in an organization to steer
away from it is difficult. For example, our software vendors and
administrators "bought into" the Windows platform and NT because of
marketing . . . and we live with the shortcommings of the platform.
The unfortunate situation is that many business execs have bought into NT so
far that it's really expensive for them to switch.
I cringe whenever I hear about a company's "clustered NT software". I
achieved more parallelism as an undergraduate using a Parallaxis virtual
machine!
Does that help?
Let me add to that:
1) Developing even simple parallel processing software, (e.g. PVM library)
for NT can easily become futile, because Microsoft routinely changes system
services so that you have to rewrite your code whenever "new functionality"
comes out.
2) The "service packs" for NT usually introduce problems for NT applications
- especially when you have several applications (all built by different)
vendors running on the same machine. Really difficult to manage multiple
products when a service pack causes some products to fail.
3) Much credit goes to Dave Cutler and crew from Digital, who helped build
NT with some of Digital's OS technology. But, the system has fallen to
cheap marketing ploys - not much substance there, folks.
4) Robert is correct about the fact that NT "clustering" products are merely
a clever approach to backup applications: if one box fails, the other picks
up the slack. A far cry from the massively parallel computations that
beowulf class machines promise (and are producing).
Richard Schilling
> -----Original Message-----
> From: Robert G. Brown [mailto:rgb at phy.duke.edu]
> Sent: Friday, October 06, 2000 4:31 PM
> To: Schilling, Richard
> Cc: 'beowulf at beowulf.org'
> Subject: RE: Why not NT clusters? Need arguments.
>
>
> On Fri, 6 Oct 2000, Schilling, Richard wrote:
>
> > Nice! This is the type of thing that corporate types need
> to hear. It is a
> > difficult task to try and convince many
> managers/supervisors why they should
> > steer away from NT. Microsoft, although they have come up short on
> > enterprise-grade "clusterable" machines, has done a great
> job of convincing
> > many execs that NT is "good enough", and attainable.
> Convincing them
> > otherwise is what you're most likely up against here.
> >
> > Great data and anecdotes is what it's going to take. . . .
> >
> >
> > Richard Schilling
> > Lake Stevens, WA
>
> You have to be careful here. I know that you understand the implied
> meaning of "clusterable" because you've been on the list a fair while
> but I'm a bit uncomfortable with the use of the word
> "cluster" as it has
> been used in the thread so far. As Greg Lindahl (IIRC)
> pointed out in a
> recent relevant thread, "clustering" means different things
> to different
> people. NT does support some very (again anecdotally, as I personally
> would rather have my teeth drilled with an almost discharged
> Black&Decker rechargable drill and a dull bit than work with any MS
> product including NT) nicely implemented failover solutions
> -- the kind
> of application where you can run the application in a distributed/load
> balanced mode and yank the plug on a box and have the application keep
> ticking.
>
> This is very different from the kind of parallel application I was
> describing (with Greg Warnes inestimable detailed quantitative help:-)
> in my previous response, the kind that is generally discussed on this
> list. It is still useful to differentiate the two in discussions with
> corporate managers to avoid being trumped by MS sales reps. If your
> job/application is computationally intensive, moderately
> tightly coupled
> (enough so that node failure causes failure of the job) and
> distributed,
> then stability becomes a critical issue unless you REALLY spend
> money/time to make your application robust to node failure. If your
> application is something like a distributed web server or DB server or
> transaction processor, the SOFTWARE is often loosely coupled
> and written
> to be robust against node failure (however expensive and
> difficult that
> was originally to accomplish). There is NT software that is indeed
> robust in this way.
>
> Linux is just beginning to come up with failover-toughened OS variants
> (e.g. Turbolinux and some variants of Red Hat) and associated
> applications. There's money there (Turbolinux is easily one
> of the most
> expensive box-set linuxes) and there will be more there, but
> this isn't
> really a traditional forte of Linux. Part of this is pure economics.
> Failover robustness is a pain in the ass to accomplish and it
> requires a
> lot of real work and investment to accomplish it. Folks
> don't even try
> unless real money is at stake, and up to a couple of years
> ago there was
> little or no "real money" in Linux. This is also
> (incidentally) one of
> the differentiating features of Extreme Linux vs Beowulfery. Extreme
> includes both beowulfery and failover clustering and other exotic
> clustering or non-clustering applications of linux and exists
> in part to
> foster the development of those applications. Beowulfery, as Greg L.
> recently pointed out, is basically high >>performance<< (as opposed to
> high reliability) computing on COTS Linux clusters. It is thus the
> best-known subset of the Extreme, but the two are not identical.
>
> A useful rule of thumb is that if you are rolling the parallel/cluster
> application yourself it is almost certainly not failover
> robust (unless
> you work quite hard and expensively to make it so) and NT
> will be a poor
> choice if it also runs for long times. Actually, NT is
> probably a poor
> choice for lots of reasons, only one of which is the robustness of the
> application. I personally would not like to develop a parallel
> application on an NT cluster because all my favorite tools are missing
> and all the tools available cost a lot of money and are highly
> nonstandard (unless you view MS's efforts in code development software
> "standard").
>
> If somebody else wrote it and made it robust against node
> failure, then
> it is a pure cost-benefit issue. If you have a choice (e.g. the
> application is available for both linux and NT) compare the
> costs of the
> application, the OS, and the admin staff for the two choices,
> since the
> failover engineering insulates you from NT's instability (in
> principle).
> You'll still almost always find the linux solution to be the
> cheaper one
> if it exists.
>
> In other cases (where maybe somebody else wrote it, but it
> isn't robust
> against node failure) you have to think a bit, but linux is
> still likely
> to be the best choice if a linux-based version of the application is
> available, because literally everything is cheaper and more
> stable with
> linux than with NT.
>
> We seem to find a theme here that is worth repeating -- Linux
> is across
> the board far cheaper than NT and is generally far more stable and
> robust at the OS level. Only if a particular clustering
> application is
> available only for NT, or if an organization is rich in NT experts so
> that there are really significant personnel costs associated with
> conversion is a deliberate selection of NT over Linux still
> worthwhile.
>
> This can happen and will continue to happen as long as there are niche
> products that "only" run on NT and as long as there are organizations
> with a stong core NT staff (and significant capital
> investment in those
> individuals).
>
> Also, much as I personally dislike MS, there are a few arenas where
> their products enjoy a decent reputation that isn't wholly
> ill-deserved.
> They just tend to be expensive (and hence cost-benefit
> losers) and very,
> very proprietary so that committing to them is like getting married to
> somebody glamourous and expensive to keep that you aren't at all sure
> that you really like. Sure they're attractive and even good
> in bed, but
> somehow you know that eventually, you're gonna pay for it...
>
> rgb
>
> [P.C.-P.S.: Please note that the previous analogy, however tasteless,
> wasn't a <it>sexist</it> analogy. I didn't specify whether the
> individual(s) involved were male, female, neither or both. I
> think that
> the experience of marrying the personality disordered but momentarily
> "beautiful/handsome/available" when one doesn't really like them and
> eventually discovering one's horrible mistake probably occurs on the
> planet of a distant star where the creatures that are mating have six
> sexes. Or even just one, in the case of a highly narcissistic (but
> evolved) species of yeast...;-)]
>
> --
> Robert G. Brown
> http://www.phy.duke.edu/~rgb/
> Duke University Dept. of
> Physics, Box 90305
> Durham, N.C. 27708-0305
> Phone: 1-919-660-2567 Fax: 919-660-2525 email:rgb at phy.duke.edu
>
>
>
>
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