[Miscellaneous] How can a rollup use multiple Data Availability layers?

[PaulRBerg]

Did you check the documentation?

• Yes

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• Yes

Issue Description

From the docs:

The Data Availability Layer defines where the raw inputs to an OP Stack based chain are published. An OP Stack chain can use one or more Data Availability module to source its input data. Because an OP Stack chain is derived from the Data Availability Layer, the Data Availability module(s) used have a significant impact on the security model of a system.

How would this work in practice? Would the data posted to both DA layers, using one of them as a backup? Or would it be posted to just one layer at a time?

[hash1go]

My understanding is OP Stack cannot handle two DA layers at the same time. Data would be posted to just one layer at a time.

cc: @sbvegan
Could you please confirm this?

[PaulRBerg]

Thank you for your answer.

If this is the case, I suggest rectifying the docs to specify that OP Stack is currently not capable of supporting more than one DA layer.

In any case - the theoretical question remains. How could a rollup handle two or more DA layers?

[hash1go]

Regarding the need to rectify the documentation, I will confirm with the OP team.

Meanwhile, according to the definition of Rollup, it needs to use a blockchain with a single consensus as both the Settlement and DA layers. Therefore, there is no rollup that handles more than one DA layer, making it necessary to consider the case of Optimium.

It is theoretically possible to adopt a backup DA layer to ensure redundancy or switch DA layers for some reason. As long as the data required to reconstruct the chain exists on an external chain, it should meet Optimium's requirements, making it an engineering problem.

As for specific changes to the OP Stack, I am not sure as it is beyond my understanding.

[sbvegan]

Hey @PaulRBerg, this page is pretty old and could use a refresh. Its older than the "created" date because we migrated docs framework. Feel free to open an issue in the docs repo and we can have our docs person take a look. At the momenet, the OP stack just supports one DA layer at a time. We're testing a beta feature for our plasma mode if you're interested in that. You could hack the op stack and modify it to use two da layers, but thats up to a curious mind to figure out.

[PaulRBerg]

Thanks for confirming @sbvegan. Created an issue in the docs repo: ethereum-optimism/docs#713

[Chomtana]

We can post hashes using the PlasmaDA standard and post data to as many DA systems as we like. Data is then fetched through a PlasmaDA proxy. (As an idea)

There is a team working on something similar to this, Plasma DA Translation Hub