Tape storage emulation for open systems environments

Abstract

A Virtual Tape (VT) server residing on a network is connectible on its front end to a plurality of heterogeneous backup hosts, with different operating systems and/or backup applications, and on its back end to one or more disk storage devices in an open systems environment. The VT server responds to tape storage commands sent by the backup host as if it were the intended tape storage device and then emulates the desired tape storage activity on the one or more disk storage devices. In a described implementation, the host and server act as SCSI initiator and target and communicate over a Fibre Channel connection.

1 . A method for storing backup data comprising: 
 a virtual tape (VT) server residing on a network and connectable to one or more disk storage devices and simultaneously connectable to multiple heterogeneous backup hosts in an open systems environment, wherein the VT server receives initiator tape storage commands sent by the hosts;    at least one backup host sending an initiator tape storage command for a target tape storage device, and wherein the VT server: 
 transparently accepts the initiator tape storage command and responds as if it were the target device; and  
 emulates the target device by converting the initiator tape storage command to a disk storage command for implementing the command with the one or more disk storage devices.  
   
     
     
         2 . A computer-implemented virtual tape storage system comprising: 
 a scalable front end connectable to a variable number of heterogeneous hosts in an open systems environment;    a scalable back end connectable to a variable number of disk storage devices; and    a target emulator and command converter which together accept tape storage commands from the hosts and implement the tape storage commands by emulating tape storage devices identified in the commands with the one or more disk storage devices.    
     
     
         3 . The system of  claim 2 , wherein the tape storage commands are Small Computer System Interface (SCSI) commands.  
     
     
         4 . The system of  claim 3 , wherein the SCSI commands are adapted for Fibre Channel (FC) transmission.  
     
     
         5 . The system of  claim 2 , wherein the tape storage devices comprise one or more of a tape library and a tape drive.  
     
     
         6 . The system of  claim 2 , wherein the one or more disk storage devices comprise one or more of a disk drive and a disk array.  
     
     
         7 . The system of  claim 2 , wherein the hosts include multiple operating systems comprising Unix and Windows.  
     
     
         8 . The system of  claim 2 , wherein at least one of the hosts has a backup application which issues the tape storage commands and serves as a single point of management and control for backup operations.  
     
     
         9 . The system of  claim 2 , wherein the system resides on a virtual tape (VT) server.  
     
     
         10 . The system of  claim 9 , wherein the VT server accepts SCSI tape storage commands.  
     
     
         11 . The system of  claim 9 , wherein the VT server includes a model describing the emulated tape devices.  
     
     
         12 . The system of  claim 11 , wherein the model describes a tape library including robotics and tape cartridges.  
     
     
         13 . The system of  claim 11 , wherein the model includes tape objects and robot objects.  
     
     
         14 . The system of  claim 9 , wherein the VT server acts as a SCSI target.  
     
     
         15 . The system of  claim 14 , wherein the target emulator identifies itself as either a SCSI stream device or a SCSI medium changer.  
     
     
         16 . The system of  claim 15 , wherein the VT server receives SCSI tape storage commands addressed to tape storage devices with logical unit numbers (LUNs).  
     
     
         17 . The system of  claim 2 , further comprising emulation data describing the emulated tape devices.  
     
     
         18 . The system of  claim 17 , wherein the emulation data has a data structure including one or more of the following fields: configuration information, robot mailbox, bin mailbox, tape mailbox, import/export mailbox, and share mailbox.  
     
     
         19 . The system of  claim 17 , wherein the emulation data has a data structure including one or more of the following fields: configuration information, cartridge directory, and cartridge data.  
     
     
         20 . A computer-readable medium containing computer-readable instructions enabling a computer to perform a method comprising: 
 accepting tape storage commands from heterogeneous hosts over channel network connections in a manner transparent to the hosts;    upon receipt of a tape storage command: 
 recording a storage location for an emulated tape storage device; and  
 storing data associated with the command on a disk storage device.  
   
     
     
         21 . A method of emulating a tape storage device comprising: 
 receiving a backup command for a designated tape storage device from a host at a virtual tape server over a network channel in an open systems environment;    the server accepting the command as the designated tape storage device and translating the backup command into a command for a disk storage device;    storing a data component of the backup command on the disk storage device pursuant to the translated command; and    recording a storage location for the stored data as an emulated tape storage device.    
     
     
         22 . A virtual tape library comprising software running on a computer including instructions for: 
 accepting a request for a tape storage device from a host over an open systems environment network;    processing the request for the tape storage device, wherein the request contains data or requests data at a tape cartridge logical address; and    storing/retrieving the data on/from a disk storage device at a recorded location which corresponds to the logical address.    
     
     
         23 . A system for storing backup data comprising: 
 a plurality of heterogeneous backup hosts with backup applications connected, in an open systems environment, to a virtual tape (VT) server by a Fibre Channel connection;    one or more physical disk storage devices connected to the VT server;    the VT server including a VT program which: 
 transparently accepts and responds to host backup initiator storage commands intended for target tape storage devices identified by a logical address;  
 converts the tape storage commands to disk storage commands to enable storage of backup data and of emulation data describing the identified tape storage devices on the one or more physical disk storage devices.  
   
     
     
         24 . A computer program with instructions for implementing a method, the method comprising: 
 accepting initiator commands from heterogeneous hosts in an open systems environment for backing up and restoring data; and    implementing as a target the initiator commands by emulating one or more tape devices with a pool of disk storage devices.    
     
     
         25 . A system for data backup comprising: 
 a backup server and a virtual tape (VT) server connected in an open systems environment;    the backup server including a backup application providing a single point of management for backup operations; and    the VT server accepting and implementing backup management requests received from the backup server which include emulating one or more tape drive or tape library devices with one or more disk storage devices.    
     
     
         26 . A method for performing backup operations comprising: 
 providing a backup server and a virtual tape (VT) server in an open systems environment;    streaming data directly from a host to a physical disk storage device via the VT server without storing the data in intermediate cache storage.    
     
     
         27 . The system of  claim 26 , wherein the VT server and disk storage device serve as primary storage for active backup data, and a physical tape storage device serves as secondary storage for the backup data.