What are the differences between chain and state database in hyperledger fabric

Question

What are the main difference between chain and state database in Hyperledger fabric. I'm confusing whether they both are same.

Answer 1

There are two place which "store" data in Hyperledger Fabric:

1. the ledger
2. the state database

The ledger is the actual "blockchain". It is a file-based ledger which stores serialized blocks. Each block has one or more transactions. Each transaction contains a read-write set which modifies one or more key/value pairs. The ledger is the definitive source of data and is immutable. The state database holds the last known committed value for any given key. It is populated when each peers validates and commits a transaction.

The state database can always be rebuilt from re-processing the ledger. There are currently two options for the state database: an embedded LevelDB or an external CouchDB. As an aside, if you are familiar with Hyperledger Fabric channels, there is a separate ledger for each channel as well.

Comments

Great info here.

How would you go about re-processing the ledger? 

Would you happen to know how long this would take?

Thanks  

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Well, that depends on the length of the chain. The lengthier the chain, the more time it takes.

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Thanks for the reply.

Thats kind of what I thought. More of  a "how long is a length of string" question.

Are there no benchmark times out there?

Why I am asking is that I am looking for information into backing up the state DB, and is it worth it?

Would you need to backup the state DB, or if there is a corruption or hardware failure, would it be quicker to reprocess the ledger and rebuild the DB?

Thanks

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There is no benchmark because it all depends on "Length of string"..

It would be quicker to reprocess the ledger but there are a lot of chances it wouldn't be successful (Lot of issues posted by people regarding this on the internet even after following the steps right)

The safer choice would be to backup the stateDB

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That's great information, much appreciated.

If I were to conduct regular backups of the state DB, and a scenario came up that I did need to perform a restore, would the DB automatically sync with the ledger, or would there be a need for additional steps in order to bring the state DB up to the correct point in time?

Thanks

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Hey.. This link should give all the details you need..

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Thanks Omkar. Was really helpful information.

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I'm glad I could help.