Patent ID: 8161133
Filing Date: 2012-04-17
Classification: G06F

Abstract:
1. A storage system, comprising: a plurality of servers; and a disk subsystem that is coupled to the plurality of servers, wherein the disk subsystem comprises: at least one logical device, and at least two file systems that are stored in the at least one logical device, wherein the servers each hold a management table that serves to manage a mount point of each file system, wherein the management table stores file system identifiers that uniquely identify the file systems within the storage system, mount point information that indicates the mount point of each of the file systems, and management server identifiers that indicate an identifier of each of the servers that manage the file systems, while sharing the same contents among the servers, wherein upon reception of a request from a client to obtain through a second server a file handle of a file, initially handled by a first server, that indicates a storage area on the disk subsystem in which data on the file within a file system is stored, a file access processing is performed such that 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, wherein said file handle includes one of said file system identifiers and an i-node number, wherein if one of said file systems is migrated to other server, the server which updates the management table and notifies all the other servers of the updated contents, wherein the file access processing includes: issuing by a the client a request to obtain a file handle of a root directory to the second server, wherein the root directory belongs to a pseudo file system for which both the first server and the second server are capable of name resolution, performing, by the second server, the name resolution of the root directory and returning the file handle of the root directory to the client, when a directory belonging to the pseudo file system exists under the root directory, issuing, by the client, a request to obtain a file system with respect to the directory belonging to the pseudo file system that exists under the root directory, and returning, by the second server, in response to the request to obtain a file system the file handle of the file system with respect to the directory belonging to the pseudo file system that exists under the root directory, when no directory belonging to the pseudo file system exists under the root directory, issuing, by the client, a request to obtain a file handle of a directory which is a mount point of a real file system below the pseudo file system, since the real file system is under management of the first server and the second server cannot perform name resolution of the directory which is a mount point of a real file system below the pseudo file system, referring, by the second server, to a mount point control table for a path relating to the real file system to send to the client a notification that the directory which is a mount point of a real file system below the pseudo file system is under management of the first server, receiving, by the client, the notification of the location of the real file system and issuing a request to obtain a file handle of the directory which is a mount point of a real file system below the pseudo file system to the first server, and then returning, by the first server, the file handle of the directory which is a mount point of a real file system below the pseudo file system to the client, using, by the client, the file handle of the file to issue a file access request to the first server and responding, by the first server, by permitting the client to access the file, wherein migration of a file system includes: upon reception of a migration instruction to migrate a file system to the second server, updating, by the first server, 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 sending at least updated contents of the management table to the second server, referring, by the second server, the updated contents of the management table sent from the first server and updating the management table held by the second server, sending, by the first server, a start notification of starting migration to the second server after receiving the migration instruction, and returning, by the first server, 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.