Network storage system with a clustered configuration sharing a namespace, and control method therefor

Abstract

Provided is a storage system as follows. A server holds a management table that serves to manage a mount point of a file system. The management table stores a file system identifier that uniquely identifies the file system within the storage system, mount point information that indicates the mount point of the file system, and a management server identifier that indicates an identifier of the server that manages the file system. The contents stored in the management table of each server are the same. Upon reception of a request to obtain a file handle, each server returns the file handle requested to be obtained. The file handle indicates, uniquely within the storage system, the storage area on the disk subsystem in which the file relating to the request is stored.

1 . A storage system, comprising: 
 a plurality of servers; and    a disk subsystem that is coupled to the plurality of servers, 
 the disk subsystem comprising:  
 at least one logical device; and  
 at least one file system that is stored in the at least one logical device, wherein:  
   the servers each hold a management table that serves to manage a mount point of the file system;    the management table stores a file system identifier that uniquely identifies the file system within the storage system, mount point information that indicates the mount point of the file system, and a management server identifier that indicates an identifier of the server that manages the file system, while sharing the same contents among the servers; and    upon reception of a request to obtain a file handle that indicates a storage area on the disk subsystem in which data on a file within the file system is stored, the servers each return the file handle that indicates, uniquely within the storage system, the storage area on the disk subsystem in which the data on the file relating to the request is stored.    
   
   
       2 . The storage system according to  claim 1 , wherein: 
 the plurality of servers comprise a first server and a second server;    upon reception of an instruction to newly create the file system, the first server creates the file system in a logical device involved in the instruction, updates the contents of the management table by adding the file system identifier, mount point information, and management server identifier that relate to the newly-created file system, and sends at least updated contents of the management table to the second server; and    the second server references the updated contents of the management table sent from the first server and updates the management table held by the second server.    
   
   
       3 . The storage system according to  claim 1 , wherein: 
 the plurality of servers comprise a first server and a second server;    upon reception of a migration instruction to migrate the file system to the second server, the first server updates the management server identifier of the management table held by the first server, which corresponds to the file system designated by the migration instruction, into an identifier of the second server, and sends at least updated contents of the management table to the second server; and    the second server references the updated contents of the management table sent from the first server and updates the management table held by the second server.    
   
   
       4 . The storage system according to  claim 3 , wherein: 
 the first server sends a start notification of starting migration to the second server after receiving the migration instruction; and    the first server returns the identifier of the second server upon receiving a file access request for the file within the file system designated by the migration instruction after sending the start notification.    
   
   
       5 . The storage system according to  claim 4 , wherein: 
 the second server mounts the file system designated by the migration instruction; and    the second server suspends the file access request upon receiving the file access request for the file within the file system designated by the migration instruction after receiving the start notification and before ending the mount.    
   
   
       6 . The storage system according to  claim 4 , wherein: 
 the second server mounts the file system designated by the migration instruction; and    the second server returns a temporary error upon receiving the file access request for the file within the file system designated by the migration instruction after receiving the start notification and before ending the mount.    
   
   
       7 . The storage system according to  claim 4 , wherein: 
 the start notification comprises a logical device identifier that identifies, uniquely within the storage system, the logical device in which the file system designated by the migration instruction is stored;    upon reception of the migration instruction, the first server copies the file system designated by the migration instruction from a copy source logical device in which the file system is stored to a copy destination logical device; and    the logical device identifier of the copy destination logical device is set to be the same as the logical device identifier of the copy source logical device held before the first server copies the file system.    
   
   
       8 . The storage system according to  claim 1 , wherein the file handle comprises a logical device identifier that identifies, uniquely within the storage system, the logical device in which the file system is stored.  
   
   
       9 . The storage system according to  claim 8 , wherein the file handle further comprises a file system number that uniquely identifies the file system within the logical device.  
   
   
       10 . A control method for a storage system that comprises a plurality of servers and a disk subsystem coupled to the plurality of servers and is coupled to client computers, 
 the disk subsystem comprising at least one logical device and at least one file system that is stored in the at least one logical device,    the plurality of servers comprising a first server and a second server,    the control method comprising the steps of:    controlling the first server to receive, from the client computer, a request to obtain a file handle that indicates a storage area on the disk subsystem in which data on a file within the file system is stored;    controlling the first server to return the file handle relating to the request to obtain a file handle to the client computer;    controlling the first server to receive, from the client computer, a file access request for the file using the file handle;    controlling the first server to access data on a file relating to the file access request within the disk subsystem by using the file handle, and to return a result of the access to the client computer;    controlling the first server, after the file system is migrated from the first server to the second server, to receive, from the client computer, a file access request for the file within the file system using the file handle, which is obtained before the migration;    controlling the first server to return a server identifier that identifies the second server to the client computer;    controlling the second server to receive, from the client computer, a file access request for the file within the file system using the file handle, which is obtained before the migration; and    controlling the second server to access data on a file relating to the file access request within the disk subsystem by using the file handle, which is obtained before the migration, and to return a result of the access to the client computer.    
   
   
       11 . The control method according to  claim 10 , wherein: 
 the servers each hold a management table that serves to manage a mount point of the file system; and    the management table stores a file system identifier that uniquely identifies the file system within the storage system, mount point information that indicates the mount point of the file system, and a management server identifier that indicates an identifier of the server that manages the file system,    the control method further comprising the steps of:    controlling the first server to receive a migration instruction to migrate the file system to the second server;    controlling the first server to update the management server identifier of the management table held by the first server, which corresponds to the file system designated by the migration instruction, into an identifier of the second server;    controlling the first server to send at least updated contents of the management table to the second server; and    controlling the second server to reference the updated contents of the management table sent from the first server to update the management table held by the second server.    
   
   
       12 . The control method according to  claim 11 , further comprising the steps of: 
 controlling the first server to send a start notification of starting migration to the second server after receiving the migration instruction; and    controlling the first server to return the identifier of the second server upon receiving the file access request for the file within the file system designated by the migration instruction after sending the start notification.    
   
   
       13 . The control method according to  claim 12 , further comprising the steps of: 
 controlling the second server to mount the file system designated by the migration instruction; and    controlling the second server to suspend the file access request upon receiving the file access request for the file within the file system designated by the migration instruction after receiving the start notification and before ending the mount.    
   
   
       14 . The control method according to  claim 12 , further comprising the steps of: 
 controlling the second server to mount the file system designated by the migration instruction; and    controlling the second server to return a temporary error upon receiving the file access request for the file within the file system designated by the migration instruction after receiving the start notification and before ending the mount.    
   
   
       15 . The control method according to  claim 12 , wherein the start notification comprises a logical device identifier that identifies, uniquely within the storage system, the logical device in which the file system designated by the migration instruction is stored, 
 the control method further comprising the steps of:    controlling the first server to copy the file system designated by the migration instruction from a copy source logical device in which the file system is stored to a copy destination logical device; and    setting the logical device identifier of the copy destination logical device to be the same as the logical device identifier of the copy source logical device held before the first server copies the file system.    
   
   
       16 . The control method according to  claim 10 , wherein: 
 the servers each hold a management table that serves to manage a mount point of the file system; and    the management table stores a file system identifier that uniquely identifies the file system within the storage system, mount point information that indicates the mount point of the file system, and a management server identifier that indicates an identifier of the server that manages the file system,    the control method further comprising the steps of:    controlling the first server to create the file system in a logical device involved in the an instruction to newly create the file system upon reception the instruction;    controlling the first server to update the contents of the management table by adding the file system identifier, mount point information, and management server identifier that relate to the newly-created file system;    controlling the first server to send at least updated contents of the management table to the second server; and    controlling the second server to reference the updated contents of the management table sent from the first server and updates the management table held by the second server.