Electrical computers and digital processing systems: support – Digital data processing system initialization or configuration
Reexamination Certificate
1999-12-13
2002-11-12
Butler, Dennis M. (Department: 2185)
Electrical computers and digital processing systems: support
Digital data processing system initialization or configuration
C713S100000, C714S006130
Reexamination Certificate
active
06480953
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to data storage systems. More particularly, the invention relates to a system, structure, and method for ensuring that a controller in a data storage system that is managed by multiple controllers, has an accurate representation of the system configuration of the data storage system.
BACKGROUND OF THE INVENTION
Disk drives in all computer systems are susceptible to failures caused, for example, by temperature variations, head crashes, motor failure, controller failure, and changing supply voltage conditions. Modern computer systems typically require, or at least benefit from, a fault-tolerant data storage system, for protecting data in the data storage system against any instances of disk drive failure. One approach to meeting this need is to provide a redundant array of independent disks (RAID).
RAID is a known data storage technology, operated by a disk array controller (controller), that uses several magnetic or optical disk storage devices, known as a disk array, working in tandem to increase disk capacity, improve data transfer rates, and provide higher data storage system reliability in the event of one or more disk storage device failures. However, not only is it desirable for a data storage system to reliably function in the instance that one or more disk storage device failures occur, it is also desirable for the data storage system to reliably function with any type of failed component, including a failed controller. For example, if a controller fails in a single controller system, the entire RAID becomes inoperable. Additionally, although failure of a single controller in RAID being managed by multiple independent controllers (such a RAID system is not shown) will not typically render the entire RAID system inoperable, such a failure will render the tasks that were being performed by the failed controller, and/or those tasks scheduled to be performed by the failed controller, inoperable.
To circumvent the system level reliability problem that all conventional single and multiple independent controller data storage systems exhibit, and to provide fault tolerance to a data storage system at a controller level, data storage systems managed by two controllers in dual active configuration were implemented.
Referring to
FIG. 1
, there is shown data storage system
124
being managed by two controllers, controllers
126
and
128
, in dual active configuration, according to a state-of-the-art. Controller
126
-
128
manage the RAID, and upon detecting that the other controller
126
-
128
has failed, will take over the tasks that were being performed by the failed controller
126
-
128
, and perform those tasks that were scheduled to be performed by the failed controller
126
-
128
. In this manner, data storage system
124
provides fault-tolerance at a controller level. The RAID in this example is the disk drive array in peripheral
140
, that includes, for example disk drives
134
-
138
.
Controllers
126
and
128
are coupled across first peripheral bus
132
, for example, an optical fiber, copper coax cable, or twisted pair (wire) bus, to a plurality of storage devices, for example, disk drives
134
-
138
, in peripheral
140
. Controllers
126
and
128
are also coupled across second peripheral bus
142
, for example, an optical fiber, copper coax cable, or twisted pair (wire) bus, to one or more host computers, for example, host computer
144
.
A first processor (not shown) in controller
126
is coupled to memory
146
that is either internal or external to controller
126
. Controller
126
maintains in memory
146
, a system configuration data structure
150
-X and a conventional system configuration update procedure (not shown) that is executable by the first processor. Similarly, a second processor (not shown) in controller
128
is coupled to memory
148
that is either internal or external to controller
128
. Controller
128
maintains in memory
148
, a system configuration data structure
152
-X and a conventional system configuration update procedure (not shown) that is executable by the second processor.
Each respective controller
126
-
128
has only one respective system configuration data structure
150
-X. For example, controller's
126
system configuration data structure
150
-X is illustrated respectively as
150
-A and
150
-B, only to reflect certain content changes that occur over time in controller's
126
system configuration data structure
150
-X due to the operation of the conventional system configuration update procedure that is discussed in greater detail below. Similarly, controller's
128
system configuration data structure
150
-X is illustrated respectively as
150
-C and
150
-D, only to reflect certain content changes that occur over time in controller's
128
system configuration data structure
150
-X due to the operation of the conventional system configuration update procedure.
Each respective system configuration data structure
150
-X represents aspects of the system configuration of data storage system
124
(“system 124”). Such aspects include, for example, information with respect to the status, structure and relationship of one or more respective components of system
124
with respect to other respective components of system
124
.
Such structural information includes, for example, an indication of whether a particular component is a disk storage device
134
-
138
, or a controller
126
-
128
. Such relationship information includes, for example, an indication that a controller
126
-
128
can communicate with a component over a particular I/O bus, such as, for example, I/O bus
132
. Such status information includes, for example, an indication of whether or not a disk storage device
134
-
138
is active, and therefore, able to process I/O requests from the controller
126
-
128
, or whether a disk storage device
134
-
138
has failed, and thus, unable to process I/O requests from the controller
126
-
128
. (Such I/O requests include, for example, Small Computer Standard Interface (SCSI) read and write data requests, which are known in the art of computer programming).
Note that system configuration
150
-A accurately represents the respective operational status of each disk drives
134
-
138
. Each disk drive
134
-
138
is illustrated as “DISK DRIVE NO. (STATUS)”, for example, DISK DRIVE
134
(ACTIVE)”, and the like. In particular, system configuration data structure
150
-A accurately represents that disk drive
134
has an active status, and accurately represents that disk drives
136
-
138
each have a respective failed status.
Data storage system's
124
system configuration (component content (structure), statuses and relationships) can change for any one of a number of reasons. For example, a system configuration can change as a result of: (a) the failure, or malfunction of a disk drive
134
-
138
; (b) the removal or replacement of a disk drive
134
-
138
in the event that the disk drive
134
-
138
failed, or was upgraded; and, (c) the moving a particular disk drive
134
-
138
to a different location in data storage system
124
, such that a different I/O bus
132
is used to communicate with the particular disk drive
134
-
138
.
Upon identifying, by a particular controller
126
-
128
, a change in the system configuration of the data storage system
124
, the particular controller
126
-
128
updates its respective system configuration
150
-X to reflect the change. (Methods of identifying changes in the system configuration of a data storage system are known in the art of computer programming). Because it is common for a particular controller
126
-
128
to detect a system configuration change of data storage system
124
without another different controller
126
-
128
detecting the same change, the particular controller
126
-
128
, upon detecting any such changes, notify each of the other different controllers
126
-
128
of the change in the system configuration. Upon receipt of such a notification, each of the r
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