[Opensim-dev] Always mutable assets in OpenSim -- does it make sense?

[Frisby, Adam]

Be careful here however,

Because if the hashing algorithm you choose ever gets 'broken' where it's possible to calculate a binary against a desired result, then people can potentially overwrite existing assets, etc.  A long hash tends to act as a good barrier against this. (256bit+ is ideal.)

Regards,

Adam

From: opensim-dev-bounces at lists.berlios.de [mailto:opensim-dev-bounces at lists.berlios.de] On Behalf Of Stefan Andersson
Sent: Wednesday, 17 December 2008 12:59 AM
To: opensim-dev at lists.berlios.de
Subject: Re: [Opensim-dev] Always mutable assets in OpenSim -- does it make sense?

First step would probably be to implement the sha-based binary store that you bring up and that we've discussed earlier, so that the immutables at least share the same binary data row. Right now, I believe we're seing massive duplication when people export/import content between worlds. Storing the binaries separately by sha key would probably be an low hanging fruit.

I would say that it's probably very much up to the service (aka 'the grid') how assets should be managed. On an grid that employs a consumer/producer division (like a fantasy game) you could probably reap dead assets quite aggressively. In a SL business model, it becomes harder, as they have to ensure consistent user experience in a heterogenous environment.

Best regards,
Stefan Andersson
Tribal Media AB

> Date: Sun, 14 Dec 2008 14:48:01 +0900
> From: mmazur at gmail.com
> To: opensim-dev at lists.berlios.de
> Subject: [Opensim-dev] Always mutable assets in OpenSim -- does it make sense?
>
> Hi,
>
> Melanie's recent thread[1] on updating assets prompted me to put in
> writing some thoughts on this topic I've been having.
>
> I'm curious whether it may be beneficial to make assets mutable. AFAIK
> assets are currently immutable because of a LL decisions early on to
> re-use one asset instance for very popular items sold no-modify. This
> makes sense for them because they can:
>
> * clean up unused assets since they own the entire infrastructure
> (regions & DBs)
> * save on space because they anticipate more identical copies rather
> than slightly modified copies
>
> Perhaps taking the opposite approach in OpenSim would be a better fit?
> I mean, copying assets when they are transferred between owners, and
> modifying them if they are modified in-world. I can see a few reasons
> this might be beneficial:
>
> * OpenSim's databases are distributed so cleaning them (reaping dead
> assets) is more difficult
> * with the advent of distributed asset servers and the long-term
> vision of a wide open 3D Internet (like HyperGrid), when an item is
> transferred in-world its assets should probably be stored in that
> avatar's own inventory DB *anyway*
> * disk is cheap, and I wonder which is more wasteful -- multiple
> copies of an asset, each differing slightly due to minor edits over
> time, or multiple copies of identical assets because they correspond
> to different objects in-world
>
> I see this as a cleaner approach to assets for the future. Sure,
> storing duplicate identical assets in a DB can be wasteful, but this
> could be alleviated with hashes of the asset or whatnot (I believe
> this was brought up on this list before).
>
> I realize this change would mean deep, possibly breaking, changes
> throughout the source code, would take a long time to hash out, etc. I
> thought I'd throw it out there anyway.
>
> Your thoughts -- or perhaps clarifications on why this absolutely
> cannot be done -- appreciated :)
>
> Thanks,
> Mike
>
> [1] https://lists.berlios.de/pipermail/opensim-dev/2008-December/004025.html
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