Re: Scalability Design Questions

Hello

We plProxy to split our database into partitions. See Kristo's blog's about
that at http://kaiv.wordpress.com/.

For replication we use Londiste in SkyTools package. SkyTools contains
several more scripts that are useful when buildin large and complex systems
running on large number of servers.

Asko

On 9/9/07, novnov <novnovice(at)gmail(dot)com> wrote:
>
>
> OK, this has been very informative and I'd like to thank the three of you.
>
> Asynchronous replication to readonly slaves is something I will look into.
> I've never touched posgtres replication; and Scott mentioned that he was
> not
> familiar with PGCluster, so there must be some other replication system
> he's
> referencing, maybe Slony-I?
>
>
> Trevor Talbot-2 wrote:
> >
> > On 9/8/07, novnov <novnovice(at)gmail(dot)com> wrote:
> >
> >> But basically, it seems that the answer to one of my questions is that
> >> there
> >> is currently no way with postgres to spread a single database over
> >> multiple
> >> servers, ala a loadbalanced apache cluster, where requests are
> forwarded
> >> to
> >> different boxes.
> >
> > Actually, that's essentially the same thing. Whether it's the front
> > end or middleware, something splits the requests apart before they're
> > processed.
> >
> > The asynchronous replication to readonly slaves Scott mentioned
> > earlier would be roughly equivalent to having several identical apache
> > boxes that have their own local copies of files that you periodically
> > rsync/ftp/whatever to them from a single place. Partitioning data
> > would be roughly equivalent to having one apache box for images, one
> > for ads, etc.
> >
> > From what I've seen people mention of RAC, it provides strong
> > guarantees about server consistency -- all of them have the changes or
> > none of them do -- but you need to go to great effort to achieve the
> > same thing on a set of apache boxes too. I mean, you don't have each
> > box accepting file uploads via the web and assume the others will
> > magically see the same file at exactly the same time, right? Unless,
> > of course, you're using them purely for CPU reasons and have a single
> > shared storage pool.
> >
> > Whatever is splitting the requests may do it on a "session" level too,
> > which makes it easier for the backend clusters. E.g. if a given user
> > always hits a given apache box, that file upload situation isn't a
> > problem as long as you can rsync faster than the sessions time out.
> > Often you need to load balance this way anyway if you have a web app
> > using an internal notion of sessions -- session data isn't replicated
> > to other apache boxes. (If you need it to be replicated, you're
> > already in special design territory, not just easy load balancing.)
> >
> > It all varies depending on the details of what you're doing. Even
> > that seemingly straightforward question isn't specific enough :(
> >
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> >
> >
>
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