[Info-vax] Current VMS engineering quality, was: Re: What's VMS up to these

[John Wallace]

On Mar 17, 7:35 pm, JF Mezei <jfmezei.spam... at vaxination.ca> wrote:
> Johnny Billquist wrote:
> > I've never seen any such thing. How would you expect each Unix instance
> > to manage the disk structure with caching and writing the same blocks as
> > another instance?
>
> isn't that why Unix shops put everything into the hands of Oracle which
> does have a DLM and does let multiple instances of an OS access the same
> databases ?
>
> Or do disk arrays really serve files via NFS  to multiple instances of
> Unix ?
>
> The thing is that the world continues to function and the sky has not
> fallen despite Unix lacking a DLM and more and more shops having
> multiple instances of Unix running at the same time.
>
> How does Google handle having 50,000 Linux nodes (or whatever number
> they have have shared access to databases ?

"How does Google handle having 50,000 Linux nodes (or whatever number
they have have shared access to databases ?"

Just about well enough that nobody important moans too much?

Google search is more like a content distribution network (or massive
wide area workstation farm) than a classical shared transactional
database. They are different problems with different solutions, so
quoting Google as an example that "UNIX scales" doesn't actually prove
much in the general case.

Google Groups is a good example of a badly designed distributed
application; stuff that you *know* is in there somewhere isn't always
accessible via the search engine. Stuff that you post may or may not
arrive in the ng. The service may or may not be available on any given
day. Whether that's UNIXes fault or Google's fault is a different
question, but illustrates that it's often high risk to quote something
Google-badged as an example of something large scale done technically
well. [As for the 'new improved' Google Groups UI: yuk. Just yuk.]

If they get a Google search (web or groups or whatever) wrong
occasionally, no one really cares (apart from anything else, the
searchers aren't the customers; the advertisers are the customers and
high volume personal information about YOU is the product they are
paying for).

If someone gets a classical transaction oriented application wrong
every now and again, people soon start to notice, especially if it's
something that involves money going to individual bank accounts e.g.
payroll.