Definitions

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domain

A domain is the top level separation of files. File keys are unique within domains. A domain consists of a set of classes that define the files within the domain. Examples of domains: fotobilder , livejournal .

class

Every file is part of exactly one class. A class is part of exactly one domain. A class, in effect, only specifies the minimum replica count of a file. Examples of classes: userpicture , userbackup , phonepost .

key

A key is a unique textual string that identifies a file. Keys are unique within domains. Examplse of keys: userpicture:34:39 , phonepost:93:3834 , userbackup:15 .

minimum replica count

This is a property of a class. This defines how many times the files in that class need to be replicated onto different devices in order to ensure redundancy among the data and prevent loss.

file

A file is a defined collection of bits uploaded to MogileFS to store. Files are replicated according to their minimum replica count. Each file has a key, is a part of one class, and is located in one domain. Files are the things that MogileFS stores for you.