Wojtek Sylwestrza
> When I hear service replication, I picture manually configuring remote
> servers
> (FTP, Web or other) and then mirroring the data from the origin server
> onto them.
>
> The first part of this process is more or less manual, and one-time
> only.
> The second task is automated and periodical/continuous.
>
> Performing these both steps allow us to provide service on the replica,
> but i'm not sure if it's necessary to have a special terminology for
> this.
>
> Do I understand service replication right, or does it have a broader
> sense ?
I intend "service replication" to mean any situation where a service is
available in more than one place. Manually set up mirroring is one example,
Joe Touch wrote:
> Prefetching or push caches can grab the copies of an
> entire server (assuming it's completely 'connected' via internal
> links) a-priori. Isn't that all prior to the request?
If it's in response to a request then I'd say it's on-demand (like
fetching a line of a memory cache). I can see the argument for calling it
a-priori, but my point is that it is a part of a response to a request, and
would never be fetched if the request were not made. Admittedly, copying
policy is very complex, and I am attempting to simplify by naming just
one dimension.
> I see the difference as a combination of all three factors
> - ahead of time
> - entire database
> - permanent copy (source invalidated, vs. timeout in a cache)
Here are some suggestions for terminology:
1. never use the word "replication" with out a modifier: service replication,
source replication, output replication
2. mirroring means source replication
3. caching means output replication
4. We chose another word, perhaps "dynamic Web caching" to mean output copying
with an on-demand copying policy, which is common practice.
5. We chose another word, perhaps "static Web mirroring" to mean a-priori
source replication, which is common practice.
6. chose other modifiers for "entire channel" and "permanent copy" as Joe
suggests. As he points out, there are many possible variants to the
policy of what get copied when, but I think this covers the major ones.
/micah
This archive was generated by hypermail 2b29 : Thu Nov 18 2004 - 11:21:26 MST