Electrical computers and digital data processing systems: input/ – Input/output data processing – Data transfer specifying
Reexamination Certificate
2000-09-28
2004-10-05
Gaffin, Jeffrey (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Data transfer specifying
C710S030000, C713S160000, C713S190000
Reexamination Certificate
active
06801960
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to computer data storage systems and, more particularly, relates to acceleration of computer data storage utilizing fibrechannel switches, disk drive aggregators, and arrays of disk drives.
BACKGROUND OF THE INVENTION
Computer systems are pervasive in our society and virtually all human activity is now influenced at least to some extent by existence and usage of these systems. The faster and more efficient these systems are, the better for all concerned. Certain computer systems developing within the technological area known as fibrechannel or fibrechannel networks do offer faster and more efficient operation, not only because of their optically-communicative capability but for other reasons as well. One of the configurations in fibrechannel networks employs multiple disk drive arrays for data storage managed by an aggregator (essentially another array but with much higher intelligence than ordinary arrays and which organizes ordinary arrays into “aggregations”) in combination with a fibrechannel switch (another intelligent device which performs a complex switching function under control of at least the aggregator). Typical inter-relationships of computer, aggregator, switch, and storage within fibrechannel networking have been established.
Referring to
FIG. 1
, there is depicted one typical fibrechannel computer system arrangement. Computer hosts
101
,
102
, and
103
communicate through fibrechannel switch or hub
104
, sometimes known as a “fabric”. The term “fabric” suggests densely-packed multiple conductors, since internal fibrechannel switch connections can be very dense. The irregularly-shaped “cloud” symbol representing the switch implies an active or changeable entity which is capable of being used or controlled. Front end fabric
104
connects to aggregator
105
(typically a RAID system, standing for Redundant Array of Independent/Inexpensive Disks) which, in turn, connects to back end fabric
106
(another fibrechannel switch or hub) to which are connected multiple disk drives
107
,
108
,
109
, and
110
. A major goal of this system is efficient movement of data or computer information from hosts to disk drive storage and vice-versa. If all computers communicate directly with all disk drives (and there can be many more than three hosts and four drives, those numbers being represented here only for purposes of clarity of illustration) then highly complex and inefficient operation with multiple hosts competing for the same storage space on the same disk drives, etc. can result. Thus, an aggregator is used to allow communication by computers with drives, but only through the aggregator to improve operation. The aggregator is a highly intelligent and complex device which appears to computers such as hosts
101
,
102
, and
103
to be a number of disk drives. The aggregator further appears to the computers to be the only disk drives in the system since it “hides” disk drives
107
-
110
connected to the back end fabric. This reduces complexity for computer hosts to a great extent. Further, this introduces a degree of security since all commands relative to data stored on disk drives from hosts must pass through, and thus be “approved” by, the aggregator. Any illegitimate command or operation may be stopped by the aggregator before it does damage. But, unfortunately, the aggregator can become a bottleneck in this configuration between computers and disk drives under certain high-traffic or busy or other conditions. Thus, the aggregating device can introduce “latency” or time delay into system operation and contribute to the very inefficiencies in system operation that it was designed to reduce or eliminate. Under certain circumstances, this can be a serious problem.
However, if the back end drives were directly accessible via the front end fabric, the aggregation “bottleneck” would be removed and certain reductions in these latencies might be achieved. In
FIG. 2
, Host computers
201
,
202
, and
203
are shown connected to front end fabric—fibrechannel switch
204
to which are also connected aggregator
208
and disk drives
205
,
206
, and
207
. It is to be understood that the number of hosts and drives are not limited to the specific number shown and that many more, or fewer, hosts and drives are intended to be represented by this diagram. In operation, any one or more of the hosts first sends data requests to the aggregator which then enables the disk drives and alerts them that these requests are coming directly to any one or more of them. Then hosts send multiple requests addressed to the disk drives through the switch directly to these different drives, accessing these drives in parallel and receiving directly back is multiple data streams in parallel through the switch, which reduces the latency factor by eliminating at least one “hop”through the aggregator. However this configuration reintroduces the security issue, because these drives, not being “protected” by the aggregator, are more exposed to illegitimate commands in this configuration. Thus, disk drives and computers in this configuration have to contain added intelligence to deal with these security issues and the task of adding this intelligence creates a more complicated and less desirable environment.
Referring next to the subject of fibrechannel protocols as further useful background information, a book entitled “Fibre Channel Volume 1 The Basics” by Gary R. Stephens and Jan V. Dedek, published by Ancot Corp, Menlo Park, Calif., first edition June, 1995, is incorporated by reference herein. Within the computer industry there are highly competitive companies which specialize in design, development and manufacture of these switches, aggregators, memory arrays, and other fibrechannel related components. If their respective designs are to be employed in the same system, or if multiple systems employing their various designs are networked together, these designs have to mesh together properly for users to derive any benefit from them. This is accomplished by having these companies agree to certain standards sometimes generically known as the “ANSI Fibre Channel Standard”. These standards are complex and are negotiated into existence by the very companies that are responsible for creating these fibrechannel-related components. One of the agreedupon products of these negotiations is what is sometimes called the “protocol stack”—five network levels of fibrechannel. (In computer networks, information or data sent between network devices is conducted on a physical level normally by electrons or photons over copper wires or fibre-optic paths respectively, and/or by telecommunication paths, and, at the same time, is also virtually conducted on multiple other network levels above the physical level.) Referring to
FIG. 3A
, five levels: FC-0, FC-1, FC-2, FC-3 and FC-4 are shown, corresponding to: physical, encode/decode (8B/10B), Framing Protocol, Common Services for Ports, and Mapping respectively. {Sometimes, another sixth layer, Upper Layer Protocol, is referred to, and is shown.} Briefly, the FC-0 functional level relates to physical connection of nodes, either optical or electrical—the nuts and bolts of connection. The FC-1 functional level relates to how information is transmitted between fibrechannel input/output ports, i.e. how lasers and electrical drivers/receivers deal with a bit stream moving into and out from a fiber. The FC-2 functional level deals with transferring information and is concerned with its content, proper arrival of content or detection of missing information or information errors; this level thus defines frame fields including frame header field layout and is utilized in embodiments of the present invention. The FC-3 functional level deals with common services that can be shared among ports. And, the FC-4 functional level handles mapping of existing non-fibrechannel interfaces for use on fibrechannel by using fibrechannel tools.
The foregoing latency problem of the prior art is addressed and relieved
Brown Jeffrey A.
Ericson George M.
Haynes, Jr. John E.
Solomon Robert C.
Chapin & Huang LLC
EMC Corporation
Huang, Esq. David E.
Sorrell Eron
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