Internally consistent file system image in distributed object-based data storage

Abstract

A system and method to perform a system-wide file system image without time smear in a distributed object-based data storage system. A realm manager is elected as an image master using the Distributed Consensus Algorithm to execute image-taking. All pending write capabilities are invalidated prior to taking the system-wide file system image so as to quiesce the realm and prepare the storage system for the system-wide image. Once the system is quiesced, the image master instructs each storage manager in the system to clone each live object group contained therein without explicitly cloning any objects contained in such object group. In one embodiment, a file manager copies an object in the system before a write operation is performed on that object after the image is taken. Neither the cloning operation nor the copying operation update any directory objects in the system. At run time, a client application may use a mapping scheme to access objects contained in the system-wide image.

1 - 61 . (canceled)  
   
   
       62 . In an object-based data storage system having a plurality of object-based secure disks (OBDs) and a storage manager facilitating data storage in one or more of said plurality of OBDs, a method of avoiding a need to rewrite metadata for an object, stored by said storage manager on one of said plurality of OBDs, when a system-wide file system image in said object-based data storage system is taken, said method comprising: 
 obtaining information identifying said file system image;    using said image identifying information, dynamically obtaining a mapping of a non-image identity of each object group appearing in a file path for said object into a corresponding identity of each said object group in said file system image; and    for each said object group in said file path for said object, dynamically substituting said corresponding identity in said file system image in place of respective non-image identity therefor when accessing a version of said object in said file system image.    
   
   
       63 . The method of  claim 62 , wherein said information identifying said file system image includes an image_ID stored in an image directory object created in said data storage system during said file system image.  
   
   
       64 . The method of  claim 63 , wherein obtaining said information includes accessing said image directory object to obtain said image_ID therefrom.  
   
   
       65 . The method of  claim 62 , wherein dynamically obtaining said mapping includes: 
 at run time, accessing each file directory object appearing in said file path for said object to obtain identity of said storage manager and said non-image identity of a corresponding object group associated therewith;    for each said object group corresponding to a respective file directory object, supplying said image identifying information, said non-image identity of said object group, and identity of said storage manager at run time to a realm manager in said object-based data storage system, wherein said realm manager is configured to maintain a record of a file storage configuration for the files stored by said storage manager; and    for each said object group corresponding to said respective file directory object, querying said realm manager at run time to obtain said mapping for said object stored by said storage manager.    
   
   
       66 . The method of  claim 65 , wherein querying said realm manager at run time includes configuring said realm manager to provide said mapping using the following information supplied thereto at run time: 
 said image identifying information;    said identity of said storage manager; and    said non-image identity of each said object group appearing in said file path for said object.    
   
   
       67 . The method of  claim 65 , wherein dynamically substituting said corresponding identity for each said object group in said file system image includes: 
 for each said object group corresponding to said respective file directory object, substituting at run time said corresponding identity thereof in said file system image in place of said non-image identity thereof; and    continuing said substitution until said version of said object in said file system image is reached.    
   
   
       68 . An object-based data storage system comprising: 
 a plurality of object-based secure disks (OBDs);    a storage manager facilitating data storage in one or more of said plurality of OBDs;    a realm manager configured to maintain a record of a file storage configuration for the files stored by said storage manager; and    an executable client application, wherein said client application, upon execution, is configured to perform the following at run time: 
 access a first OBD to obtain identity of a system-wide file system image from an image directory object stored thereon, and  
 obtain a mapping from said realm manager of each object group corresponding to a respective file directory object in a file path for an object stored by said storage manager on a second OBD, wherein said realm manager maps a non-image identity of each said object group into a corresponding identity of each said object group in said file system image.  
   
   
   
       69 . A computer-readable storage medium containing a program code, which, upon execution by a processor in an object-based distributed data storage system, causes said processor to perform the following at run time to access an image version of an object stored in said data storage system: 
 obtain information identifying a system-wide file system image in said data storage system;    using said image identifying information, obtain a mapping of a non-image identity of each object group appearing in a file path for an object stored in said data storage system into a corresponding identity of each said object group in said file system image; and    for each said object group in said file path for said object, substitute said corresponding identity in said file system image in place of respective non-image identity therefor when accessing said image version of said object in said file system image.