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RAID Storage System Hierarchical Global Sparing Architecture using Spare Pools to Enable DDM Class Intermix (i.e.; FC-AL, SATA, SAS) within a Storage System

IP.com Disclosure Number: IPCOM000032744D
Original Publication Date: 2004-Nov-11
Included in the Prior Art Database: 2004-Nov-11
Document File: 2 page(s) / 96K

Publishing Venue

IBM

Abstract

Direct access storage device (DASD) storage systems that manage multiple RAID arrays typically limit their underlying storage devices to a particular protocol class/type. DASD RAID controllers that use global sparing need methods/rules to determine what storage devices are spare candidates for particular RAID arrays. Allowing storage device intermix that goes beyond different size and speed (i.e.; FC-AL, SATA, SAS) within the same global sparing domain can create reliability and performance issues with RAID array sparing scenarios. Disclosed is a system that uses the concept of spare pools to enable a layer of segmentation of different classes of DDMs to provide a first order hierarchy of global RAID array sparing within a RAID Array Class to enable intermix within the same storage system. In some situations a user may want to allow a sparing action to occur from one drive type/class to another creating a DDM intermix within the same RAID array (FC-AL to SATA), but not allow the sparing action to occur in the opposite direction (SATA to FC-AL). To enable this type of sparing hierarchy, add an additional layer of hierarchical ordering rules to govern the interaction between the spare pools and spare candidate selection.

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RAID Storage System Hierarchical Global Sparing Architecture using Spare Pools to Enable DDM Class Intermix (i.e.; FC-AL, SATA, SAS) within a Storage System

Disclosed is a system and method to manage and control a policy based hierarchical structure intermix of storage device technologies within a RAID storage system. The diagram below is a visual representation of a structure that allows implementation of a system global sparing policy that allows drive class intermix within a system providing a first order level of isolation in sparing scenarios. The primary affinity of RAID arrays of a particular storage device class is to a pool of spare devices within its' own class maintaining the same performance and reliability characteristics of the class when a sparing action occurs. Within each spare pool a hierarchy of preferential spare candidate ordering rules can be established to determine in what order spare candidates are selected for a failure within each RAID class array. To enable a higher order utilization of available storage devices that have been allocated/designated as spares, each spare pool is assigned an affinity to a set of inter-spare pool preferential ordering rules. The pool level affinity is used to allow rules to be defined that govern the intermix of storage device classes to be used in determining how spare candidates can be utilized in a cross device RAID Array class. This invention applies to situations where the same interconnect protocol is used to connect/intermix different storage device classes within a topology that can result in the different device classes residing on the same communications network (i.e; a FC Network is used...