CAP Theorem for Seaweed-FS

[mohamm...@gmail.com]

Hi,

CAP Theorem says each system maintain at last two of three from Availability, Consistency and Partition tolerance.

Anybody knows Weed-FS stands in which step? It preserves CA, CP or AP?

Thanks,

Mohammad

[Chris Lu]

For writes, CP. For reads, AP.

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[mohamm...@gmail.com]

Thanks for you answer,

Can you refer these concepts within the code you have implemented or your documentation or give me a link which CP and AP are mentioned?

[Chris Lu]

During writes with replication, multiple copies of the data are sent to multiple volume servers, and the operation will only return successfully if all copies are written successfully.

The reads are actually implemented by the read client. Most commonly, after a volumeId lookup, a list of all the data locations are returned. Usually you just use one of the data locations to read or compose a URL. There are no data consensus checking.

Technically you can implement more checking during reads. But it is not necessary, since for consistency R + W > N (read replica count + write replica count > replication factor), the read count is always 1, the write count is always N, and 1+N is always greater than N.

Chris