Storage device and storing method

Abstract

To enable a capacity of an entire storage device to be kept by adding a flash drive or a flash module in the flash drive for a flash memory that has a failure, even if the storage device using the flash memory has a failure in its part such as a part of flash memory chip has a failure, for example, the flash memory chip has run out of its lifetime. In a storage device equipped with two or more memory device units with a plurality of semiconductor memory devices, each of which has a functional capacity unit smaller than a capacity of an entire semiconductor memory device and has a writing lifetime for each functional capacity unit, only a functional capacity unit whose writing lifetime is run out to be determined as unable to be written is substituted by a functional capacity unit in a memory device of the other memory device unit to keep a predetermined capacity of the entire device.

1 . A storage device comprising:
 a Redundant Array of Independent Disks (RAID) controller unit controlling read request and write request from a host unit; and   a storage unit comprising a plurality of flash drives configured as a RAID group each comprising a drive controller and a plurality of flash memory devices in which a functional capacity unit is smaller than an entire capacity of the flash memory devices and includes a writing lifetime for each functional capacity unit,   wherein the drive controller of a first flash drive belonging to the RAID group determines at least one functional capacity unit of the flash memory devices whose writing lifetime exceeds a predetermined value and replaces determined functional capacity unit by a functional capacity unit of flash memory devices of a second flash drive,   wherein the second flash drive is added to the RAID group,   wherein the RAID controller unit sends the logical address corresponding to read request from the host unit to the each flash drives belonging to the RAID group,   wherein the each drive controller sends whether the flash memory device stores data corresponding to the logical address or not, and   wherein the RAID controller unit receives the signals from the flash drives and restores the data requested from the host unit.   
     
     
         2 . The storage device according to  claim 1 , wherein the RAID controller unit determines to restore the data or send error to the host unit based on the number of signals indicating the flash memory device stores data corresponding to the logical address. 
     
     
         3 . The storage device according to  claim 2 , wherein when the RAID controller unit receives the signals from the flash drives, the RAID controller selects a latest data and restores the data requested from the host unit. 
     
     
         4 . The storage device according to  claim 1 , wherein when the RAID controller unit writes the data, the RAID controller unit selects flash drives belonging to the RAID group for sending logical address and data to the flash drives. 
     
     
         5 . The storage device according to  claim 1 , wherein the drive controller converts physical address information for accessing the flash memory devices and logical address information. 
     
     
         6 . A method in a storage device which includes a Redundant Array of Independent Disks (RAID) controller unit controlling read request and write requests from a host unit, and a storage unit having a plurality of flash drives configured as a RAID group each including a drive controller and a plurality of flash memory devices in which a functional capacity unit is smaller than an entire capacity of the flash memory devices and includes a writing lifetime for each functional capacity unit, said method comprising:
 determining, by the drive controller of a first flash drive belonging to the RAID group, at least one functional capacity unit of the flash memory devices whose writing lifetime exceeds a predetermined value and replaces the determined functional capacity unit by a functional capacity unit of flash memory devices of a second flash drive;   adding the second flash drive to the RAID group;   sending sends the logical address corresponding to read request from the host unit to the each flash drives belonging to the RAID group;   sending, by each drive controller, whether the flash memory device stores data corresponding to the logical address or not; and   receiving the signals from the flash drives and restoring the data requested from the host unit.   
     
     
         7 . The method according to  claim 6 , further comprising:
 determining to restore the data or send error to the host unit based on the number of signals indicating the flash memory device stores data corresponding to the logical address.   
     
     
         8 . The method according to  claim 7 , further comprising:
 when the signals are received from the flash drives, selecting a latest data and restoring the data requested from the host unit.   
     
     
         9 . The method according to  claim 6 , further comprising:
 when the data is written, selecting flash drives belonging to the RAID group for sending logical address and data to the flash drives.   
     
     
         10 . The method according to  claim 6 , further comprising:
 converting physical address information for accessing the flash memory devices and logical address information.