Virtual storage devices

Abstract

Accessing stored data includes providing a virtual storage area having a table of pointers that point to sections of at least two other storage areas, where the virtual storage area contains no sections of data, in response to a request for accessing data of the virtual storage area, determining which particular one of the other storage areas contain the data, and accessing the data on the particular one of the other storage areas using the table of pointers. Accessing stored data may also include associating a first one of the other storage areas with the virtual storage area, where the virtual area device represents a copy of data of the first one of the other storage areas. Accessing stored data may also include causing all of the pointers of the table to initially point to sections of the first one of the other storage areas when the virtual storage area is initially associated with the first one of the other storage areas. The storage areas may be storage devices. The sections may be tracks.

1 - 38 . (canceled)  
   
   
       39 . A method handling an initial data write to a storage area for which a point-in-time copy of stored data has been provided using a virtual storage area having a table of pointers that point to sections of the stored data and to sections of at least one other storage area, the method comprising: 
 copying the section of stored data from the storage area to a section of the at least one other storage area prior to the write;    causing a pointer of the virtual storage area to point to the section of the at least one other storage area; and    writing the new data to the section of the stored data.    
   
   
       40 . A method, according to  claim 39 , wherein all of the pointers of the table are initialized to point to the stored data.  
   
   
       41 . A method, according to  claim 39 , wherein prior to copying data to a section of the at least one other storage area, the section of the at least one other storage area is maintained as a free section containing no data.  
   
   
       42 . A method, according to  claim 41 , further comprising: 
 maintaining a doubly linked list of all free sections of the second one of the other storage areas.    
   
   
       43 . A method, according to  claim 39 , further comprising: 
 associating a data indicator with sections of the stored data, wherein the data indicator for a particular section indicates whether a write operation has been performed to the particular section after creation of the virtual storage area.    
   
   
       44 . A method, according to  claim 43 , further comprising: 
 in response to a write to a first section of the stored data and the data indicator indicating that no write operation has been performed to the first section, copying data of the first section to a second section that is on the at least one other storage area and causing a corresponding one of the pointers of the table to point to the second section.    
   
   
       45 . A method, according to  claim 44 , further comprising: 
 following copying the data from the first section to the second section, sending status information to a device that caused the write operation to be performed.    
   
   
       46 . A method, according to  claim 44 , wherein prior to copying data from the first section to the second section, the second section is maintained as a free section containing no data.  
   
   
       47 . A method, according to  claim 46 , further comprising: 
 maintaining a doubly linked list of all free sections of the second one of the other storage areas.    
   
   
       48 . A method, according to  claim 39 , wherein each of the sections of data is a track of data.  
   
   
       49 . A method, according to  claim 39 , wherein each of the storage areas is a storage device.  
   
   
       50 . A computer program product, provided in a computer-readable storage medium, that handles an initial data write to a storage area for which a point-in-time copy of stored data has been provided using a virtual storage area having a table of pointers that point to sections of the stored data and to sections of at least one other storage area, the computer program product comprising: 
 executable code that copies the section of stored data from the storage area to a section of the at least one other storage area prior to the write;    executable code that causes a pointer of the virtual storage area to point to the section of the at least one other storage area; and    executable code that writes the new data to the section of the stored data.    
   
   
       51 . A computer program product, according to  claim 50 , further comprising: 
 executable code that associates a data indicator with sections of the first one of the other storage areas, wherein the data indicator for a particular section indicates whether a write operation has been performed to the particular section after creation of the virtual storage area.    
   
   
       52 . A computer program product, according to  claim 51 , further comprising: 
 executable code that sends status information to a device that caused the write operation to be performed following copying the data from the first section to the second section.    
   
   
       53 . A computer program product, according to  claim 50 , wherein each of the sections of data is a track of data.  
   
   
       54 . A computer program product, according to  claim 50 , wherein each of the storage areas is a storage device.