Patent ID: 6470421
Filing Date: 2002-10-22
Classification: G06F

Abstract:
In a subsystem including access means responsive to external commands for writing onto or reading cylindrically addressable, sector-organized tracks of variable-length formatted (CKD) records including parity images of predetermined ones of said CKD tracks from an array of fixed block formatted, multitracked disk drives (HDDs), said access means including means for writing said CKD record and parity image tracks on the HDDs in a predetermined order until the cylinder of addresses is exhausted, whereby the subsystem further comprises:(a) means for ascertaining whether any tracks and parameters specified in any external commands are indicative of either a full CKD track operation, span more than a single CKD track, or sequential operations; (b) means for interpreting each access command by either (i) converting the CKD sector address range into a fixed-block address range defining a partial CKD track inclusive of the first data byte of the starting CKD sector and the last data byte of the last CKD sector in the event that the tracks and parameters specified in the access commands are not indicative of either a full CKD track operation, span more than a single CKD track, or sequential operations, or (ii) converting the CKD sector address range into a fixed-block address range defining full CKD tracks; and (c) means for accessing the fixed blocks in the converted range from the counterpart HDDs in the array, and for staging the accessed blocks as either a partial or full CKD track or tracks to the subsystem, wherein the array of HDDs is organized and operated as a RAID 5 array of HDDS, and further wherein the predetermined order for causing the CKD tracks and parity images to be stored on the HDDs is a round robin order, and still further wherein the recording capacity of each HDD track exceeds the byte length of any track of CKD-formatted records in the cylinder.