Hierarchical RAID system including multiple RAIDs and method for controlling RAID system

• US 20020124139A1
• Filed: 03/28/2001
• Published: 09/05/2002
• Est. Priority Date: 12/30/2000
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Baek, Sung-Hoon, Ahn, Dae-Young
• Granted Patent: US 6,651,137 B2
• Time in Patent Office: Days
• US Class Current: 711/114
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 2211/1045 Nested RAID, i.e. implementing a RAID scheme in another RAID scheme
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems

Abstract

In a data storage system based on large capacitance, high performance and high availability through a hierarchical construction of redundant arrays of expensive disks (RAID) and a method for controlling the storage system, in order to provide better reliability and more prominent performance than the traditional RAID, and more particularly, in a hierarchical RAID system provided with a plurality of RAIDs in which at least one RAID composed of a large number of disks is used as a virtual disk, and a method for controlling the RAID system, and further in a record medium capable of being read through a computer having a writing of a program to realize the inventive method; the hierarchical RAID system includes a host computing unit; at least one upper level RAID controlling unit having a first RAID Level X, for controlling a plurality of first lower level RAID controlling units having a second RAID Level Y in order to use a lower level RAID as a virtual disk; and the plurality of first lower level RAID controlling units having the second RAID Level Y, for controlling numerous member disks under a control of the upper level RAID controlling unit so as to be used as the virtual disk of the upper level RAID.

Claims

1. A hierarchical RAID system having a plurality of RAIDs, in which at least one RAID having a large number of disks is used as a virtual disk, said hierarchical RAID system comprising:

a host computing unit;

at least one upper level RAID controlling unit having a first RAID Level (X), which is coupled to the host computing unit; and

a plurality of first lower level RAID controlling units having a second RAID Level (Y), each of which is controlled by the upper level RAID controlling unit and includes member disks.

2. The system as recited in claim 1, wherein at least one of the first lower level RAID controlling units includes zero or more second lower level RAID controlling unit having a third RAID Level Z (Z denotes a lower level than the second level) and controlling member disks.

3. The system as recited in claim 2, wherein at least one of the second lower level RAID controlling units includes zero or more third lower level RAID controlling unit having a fourth RAID Level (the fourth RAID level is lower than the third level) and controlling member disks, such that said hierarchical RAID system can be extended to a deeper level than the fourth level.

4. The system as recited in claim 1, wherein in the hierarchical RAID system having the plurality of RAIDs based on a level depth 2, the upper level RAID Level X and the first lower level RAID Level Y respectively is any one traditional RAID Level number out of 0, 1, 3, 5 and 6.

5. The system as recited in claim 4, wherein a hierarchical RAID Level (X×

Y) having the upper level RAID Level X and the lower level RAID Level Y is any one out of 0×

3, 0×

5, 3×

1, 5×

1, 5×

5, 5×

6, 6×

5 and 6×

6, in said hierarchical RAID system having the plurality of RAIDs based on the level depth 2.

6. The system as recited in claim 5, wherein the hierarchical RAID system having the hierarchical RAID Level X×

Y of 5×

5 tolerates against at least three-disk failures and at most (i+j+1)-disk failures, the i being the number of virtual disks constructing the upper level RAID and the j being the number of actual disks constructing each of the lower level RAID.

7. The system as recited in claim 6, wherein the disk utilization of the hierarchical RAID Level 5×

5 is (i1)(j−

1)/(ij), the i being the number of virtual disks constructing the upper level RAID and the j being the number of actual disks constructing each of the lower level RAID.

8. The system as recited in claim 2, wherein in the hierarchical RAID system having the plurality of RAIDs based on a level depth 3, the upper level RAID Level X, the first lower level RAID Level Y and the second lower level RAID level Z respectively have any one traditional RAID Level number out of 0, 1, 3, 5 and 6.

9. The system as recited in claim 8, wherein in the hierarchical RAID system having the plurality of RAIDs based on the level depth 3, a hierarchical RAID Level (X×

Y×

Z) having the upper level RAID Level X, the first lower level RAID Level Y, and the second lower level RAID Level Z is any one out of 1×

5×

5, 1×

3×

3, 1×

6×

6, 1×

5×

6, 1×

6×

5, 5×

5×

5, 3×

3×

3, and 6×

6×

6.

10. A method for controlling a hierarchical RAID system having a plurality of RAIDs in which at least one RAID composed of a large number of disks is used as a virtual disk, said method comprising the steps of:

a) giving a read-command of data and parity from a upper level RAID controlling unit to a lower level RAID controlling unit when a write-command for new data is given from a host computer;

b) performing an exclusive OR of the new data, existing data and the parity, and executing a write-transmission in the lower level RAID controlling unit so as to perform a renewal of the parity and the data according to the execution result of the exclusive OR operation;

c) generating a command for reading the parity and data of a hard disk in the lower level RAID controlling unit according to the read-command of the step a), and transmitting it to the upper level RAID controlling unit; and

d) leading a reading for the data and a parity value and performing the exclusive OR according that the write-command given from the upper level RAID controlling unit becomes a write-transmission of each corresponding lower level RAID controlling unit, and executing the write-transmission for the renewal of parity and data.

11. A record medium capable of being read through a computer so as to use at least one RAID having a large number of disks as a virtual disk, in a hierarchical RAID system having a microprocessor, the record medium characterized in that the computer has a writing of a program to realize:

a first function of giving a read-command for data and parity from a upper level RAID controlling unit to a lower level RAID controlling unit when a write-command for new data is given from a host computer;

a second function of performing an exclusive OR of the new data, existing data and the parity, and executing a write-transmission in the lower level RAID controlling unit so as to perform a renewal of the parity and the data according to the execution result of the exclusive OR operation;

a third function of generating a command for reading the parity and data of a hard disk in the lower level RAID controlling unit according to the read-command of the first function, and transmitting it to the upper level RAID controlling unit; and

a fourth function of evoking a reading for the data and a parity value and performing the exclusive OR according that the write-command given from the upper level RAID controlling unit becomes the write-transmission of each corresponding lower upper level RAID controlling unit, and executing the write-transmission for the renewal of parity and data.