[Novalug] Software-based load balancing
plarsen at famlarsen.homelinux.com
Fri Mar 9 09:43:53 EST 2012
On Thu, 2012-03-08 at 00:03 -0500, Omniplex wrote:
> Phone sucks for inline responses.
> I think we are probably in agreement mostly then based on your statements. However our DBs are in a different zone behind the secure zone and we have additional firewalls between all the zones. The data is also not all stored in a database directly accessible from the secure zone servers. Sometimes they will need to make a web services call to something else or a connection to a different set of databases.
Let me be a bit more clear when we talk databases. A database is not
just a database. It has a purpose. With quite a few technologies, like
rules, SOA, Portal etc. etc. we have METADATA storages. On the other
hand, we have operational data else-where. The two don't mix. The reason
is, that metadata is so tightly integrated into the server, ie my
business rules server metadata has to be in sync with the exact
version/patch level I have on the business rules server. Also, as a
developer I will NEVER EVER access the metadata server directly. I will,
however access the operational data directly.
For this reason, the DB that goes with the business rules server would
be located DIRECTLY ON THE HOST that does the business rules. One get
patched means the other gets patched. It also means, that for clustering
reasons I do replication between the nodes (with Java we have a lot of
technologies to do this easily through JCRs like ModeShape). For this
reason, I don't see the backend storage for my business rules to be on
part with my operational data and hence, not a separate tier.
Operational data is a different story. Many times it's not owned by "my"
project and I share it with other projects. So it automatically because
a tier in itself, fully isolated behind separate walls etc. Even if I
use federated datamodels I have to take into account that the data is
not "local" and I may need to look at local caching for optimization and
a lot of other issues. So my 3 tier model easily becomes more tiers as I
add external operational data access.
> Our presentation zone runs about 45 servers for this example and a similar number of secure zone servers. Separation for both performance and security is a requirement.
Ahh yes. Again, scaling out groups piece-meal is necessary as you scale
out. It allows you to trim a server to specific services only, less
overhead and easier to optimize and patch. So if your app has 100s of
APIs you may have group with a small subset of those APIs implemented,
and again the LB's responsibility is to know which groups implement what
Systems like Amazon and Facebook have to do this - you cannot implement
all features on a single server and expect easy scaleout and fast
Wise words of the day:
BTW: I have a better name for the software .... Microsoft Internet
-- George Bonser
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