	US 7,596,673 B2
	Failure tolerant data storage
Christopher Jensen Read, San Diego, Calif. (US)
Assigned to Sony Corporation, Tokyo (Japan); and Sony Electronics Inc., Park Ridge, N.J. (US)
Filed on Dec. 08, 2005, as Appl. No. 11/297,271.
Prior Publication US 2007/0136525 A1, Jun. 14, 2007
Int. Cl. G06F 12/16 (2006.01)

U.S. Cl. 711—170 [711/114; 711/161]

12 Claims

1. A method of allocating storage for storing data across a plurality of N storage devices S₁. . . S_N, wherein at least one of the storage devices has a storage capacity that is not equal to a storage capacity of others of the storage devices, the method comprising:

a) determining a maximum capacity C_MAXof a storage device S_MAXhaving a largest capacity of the plurality of storage devices S₁. . . S_N;

b) determining a total storage capacity C of all of the plurality of storage devices

where K is a counting integer;

c) defining a maximum total number of fountain codewords

that could be stored in the plurality of storage devices S₁. . . S_N;

d) defining F_MAXas a maximum number of fountain codewords that would be lost if the data in S_MAXis lost;

e) estimating a target ratio of capacity to fountain codewords V as V≈C/F≈(C−C_MAX)/(F−F_MAX)≈(C−C_MAX)/R, where R is a number of fountain codewords required to recover C_MAXif the data in S_MAXis lost;

f) using the estimate of the value of V to estimate the values of F₁. . . F_Nas F_K=Int(C_K/V);

g) adjusting the estimated values of F₁. . . F_Nby addition of a rounding factor F_K=Int(C_K/V+L) to assure that

and

h) allocating fountain codewords, and storing data to the storage devices S₁. . . S_Nin proportion to the estimated values of F₁. . . F_N.