Capacity expansion method and device

A capacity expansion device, comprising:

• a processing unit, configured to divide, in a distributed RAID system, each hard disk into virtual hard disks of equal size equally, wherein the quantity of the virtual hard disks is an integer multiple of m, wherein m is the maximum quantity of RAID groups that can be constructed in the distributed RAID system and m is a positive integer;
• wherein the processing unit is further configured to divide the original hard disk into X groups equally, wherein X is the quantity of units of each strip in the distributed RAID, system, the quantity of original hard disks in the distributed RAID system is an integer multiple of X, and X is a positive integer;
• a selecting unit, configured to select m virtual hard disks from each hard disk to form one original hard disk, wherein all the original hard disks form one original hard disk group;
• wherein the selecting unit is further configured to select m virtual hard disks from each original hard disk group in sequence to form one virtual hard disk group;
• an inserting unit, configured to insert, in the distributed RAID system, an added hard disk formed by virtual hard disks with the quantity being an integer multiple of m, wherein the quantity of the added hard disks is an integer multiple of X;
• wherein the selecting unit is further configured to select m virtual hard disks from each added hard disk, and insert the m virtual hard disks into the virtual hard disk group;
• and
• the processing unit is further configured to move, in the virtual hard disk group, data in virtual hard disks of the original hard disk to the virtual hard disks of the added hard disk.