[sldev] [SVC] What is a Grid? (Searching for a hard definition)

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zai

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Feb 4, 2009, 7:44:51 PM2/4/09
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Hey there!

I wrote a Wiki article about 'Land' which goes from parcel to region to
estate to grid. When I came to grid, I realized that I had no real idea
how to pin it.
The current definition there is
"A collection of sims (e.g. Agni & Aditi) with a shared asset database."
Does that come close to reality? Can someone improve it?

The article is located at
https://wiki.secondlife.com/wiki/Land

Greetz,
zai


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Gareth Nelson

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Feb 4, 2009, 7:55:04 PM2/4/09
to zai, sl...@lists.secondlife.com
In the context of SL:
A collection of servers which collectively work together to provide
the services required to operate a full virtual world.

Escort DeFarge

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Feb 5, 2009, 12:12:22 AM2/5/09
to sl...@lists.secondlife.com
For an accurate definition -- start here...

http://en.wikipedia.org/wiki/Open_Grid_Services_Architecture

...the SL architecture doesn't actually conform to a strict definition
of "grid computing" as you'll soon see. However, the SL grid does have
one big thing going for it -- it works (mostly).

/esc

Meadhbh Hamrick (Infinity)

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Feb 5, 2009, 12:49:35 AM2/5/09
to Escort DeFarge, sl...@lists.secondlife.com
right. i think we're less in the WSDL camp and more in the REST camp,
so we might say that OGSA is a _type_ of a grid, but that we adhere
more to something like what's defined in http://en.wikipedia.org/wiki/Grid_computing
with REST semantics layered on top of our services.

zai

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Feb 5, 2009, 1:19:09 AM2/5/09
to sl...@lists.secondlife.com
eeps, that one went off list... again:


eerrr... I see I should clarify.
So the question I meant was: What is meant by the word "Grid" in context
to SL, in some easy understandable way so it fits in the

https://wiki.secondlife.com/wiki/Land#Grid

article. (Please don't answer with a link to
http://secondlifegrid.net/ )

We got:
Gareth:


"A collection of servers which collectively work together to provide
the services required to operate a full virtual world."

Dahlia (off-list reply):
How about something along the lines of "A collection of 256x256x(some
big number) regions arranged on a cartesian plane which share common
back end support services such as asset and inventory storage, presence,
and communications."

as well as the two Wikipedia links and the initial definition I used in
the article.

I think Gareth is something intuitivly understandable although maybe not
very specific. In Dahlias version, the numbers are confusing me. Can a
grid contain of just one region? I guess it can...

I got confused when a friend mentioned that OpenSim got StandAlone- and
Grid-mode so what is a sim _without_ a grid... Sorry to bother this list
with my pondering as it won't help with developement and is just some
documentation issue.

Greetz,
zai

Tateru Nino

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Feb 5, 2009, 2:30:34 AM2/5/09
to zai, sl...@lists.secondlife.com
Well, that only really works for SL style grids. The virtual environment
grids from the 80's and 90's are a bit different, and it isn't
unreasonable to see other kinds of grids out in the industry as time
goes.

On Thu, 2009-02-05 at 01:44 +0100, zai wrote:
> Hey there!
>
> I wrote a Wiki article about 'Land' which goes from parcel to region to
> estate to grid. When I came to grid, I realized that I had no real idea
> how to pin it.
> The current definition there is
> "A collection of sims (e.g. Agni & Aditi) with a shared asset database."
> Does that come close to reality? Can someone improve it?
>
> The article is located at
> https://wiki.secondlife.com/wiki/Land
>
> Greetz,
> zai
>
>

_______________________________________________

ordinal....@fastmail.fm

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Feb 5, 2009, 4:23:17 AM2/5/09
to zai, sl...@lists.secondlife.com
I think the current definition is quite good, for SL. I have been
having to explore the concept of "grid" in relation to both SL and
opensims and, more specifically, the opensim "hypergrid" system, and
what I have come down to is "the combination of (a) one or more region
and (b) overall identity, asset management and other global systems".

Of course, opensim and SL deal with issues in different ways in any
case so exactly what is done by (a) and what by (b) will be different.
And the hypergrid thing splits everything up into multiple (a)s and
(b)s, hosted anywhere you like. But if I was trying to explain what
"the Grid" was to somebody new and not very technical, I would be
waffling along the lines of "it's made up of regions, which are laid
out in a grid pattern, and each region has an individual program that
handles things that happen in that region - and there are also
underlying databases to handle things that aren't tied to a region,
like your inventory. And they all talk to each other."

Escort DeFarge

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Feb 5, 2009, 11:55:39 AM2/5/09
to Meadhbh Hamrick (Infinity), sl...@lists.secondlife.com
I strongly support LL's decision to favor REST over WSDL (for many, many
reasons).

For sure, OGSA is definitely only one type of grid, but otoh that does
not make SL a "grid computing environment".

Wikipedia's Grid Computing entry has loosened considerably over the last
3-4 years. To my mind/taste, when defining "grid computing", the tighter
and clearer definition stated in the short paper "What is the Grid"
(http://www-fp.mcs.anl.gov/~foster/Articles/WhatIsTheGrid.pdf) remains a
much more helpful and accurate definition. Of the three checkpoints in
that definition only (3) probably counts for SL's current grid
architecture, since the LL grid has resources under central control (1),
and is not open (2). (Though I note that the AWG is definitely moving SL
closer to this definition).

For most, I sure this is all an exercise in hair-splitting, but I find
it hard to state that SL is a grid computing environment (as yet) but
rather I would say that it is an highly distributed system that includes
a grid.

/esc

Kent Quirk (Q Linden)

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Feb 5, 2009, 12:50:14 PM2/5/09
to Second Life Developer Mailing List
And whether or not SL strictly fits some external definition of "grid
computing", we use the term Grid within Second Life, which is what the
OP was asking for.

In that context, the Second Life grid is the integrated system that
provides a networked collection of servers, some of which are
simulators that implement our presentation of land. Those are arranged
in the form of a rectangular mesh (but yes, it would be possible to
have a "grid" with only one simulator in it). In addition, the SL grid
provides a set of other services, including presence, inventory
management, and asset store, that integrate with but are independent
of the simulators.

Q

Dahlia Trimble

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Feb 5, 2009, 12:51:54 PM2/5/09
to zai, sl...@lists.secondlife.com
The numbers I had in my (mistakenly private) reply were describing the size of a single region on a grid of regions, as implemented in SL. My answer was also intended as a lay answer, as the term "grid" has multiple meanings and may not be necessarily interpreted by laity as a "grid computing environment"

Joshua Bell

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Feb 6, 2009, 1:31:23 PM2/6/09
to Second Life Developer Mailing List
Even within SL there are some different uses of "grid". One that springs
to mind is "Main Grid" vs. "Teen Grid". These would be considered the
same "grid" via Q's definition below as they are implemented on the same
physical hardware and core services (i.e. "agni"). The intent, however,
is that they are not causally connected (i.e. nothing on one can affect
another).

zai

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Feb 10, 2009, 10:31:32 AM2/10/09
to Kent Quirk (Q Linden), Second Life Developer Mailing List
I'm very late with this answer, but better late than never ^^
I added Q's definition to the article and linked a reference to this
discussion in case the reader is searching for further info.

https://wiki.secondlife.com/wiki/Land#Grid

Just wanted to thank for the replies! They were really
helpful/interesting. =)

Cyas,
zai

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