Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
2000-03-23
2002-10-15
Elmore, Reba I. (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C711S161000
Reexamination Certificate
active
06467034
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data mirroring method, and more particularly to a data mirroring method and an information processing system for smoothly mirroring data in backing up data.
2. Related Art
A conventional data mirroring method is disclosed for example in U.S. Pat. No. 5,742,792, entitled “Remote Data Mirroring”, and is described with reference to FIG.
5
.
In
FIG. 5
, a site A is composed of a host A
12
and a main data storage system
14
and a remote site B remotely controlled is composed of a host B
52
and an auxiliary data storage system.
The main data storage system
14
is composed of a controller
16
and a storage unit
20
, and the auxiliary data storage system
46
is composed of a controller
44
and a storage unit
48
.
And the controllers
16
and
44
are respectively composed of channel controllers
26
and
54
for sending and receiving data to and from the hosts
12
and
52
, data controllers
32
and
68
for controlling internal buses
38
and
70
, caches
28
and
64
for temporarily writing and reading data, communication controllers
36
and
42
for sending and receiving data between the site A and the remote site B, and disk controllers
30
and
66
for sending and receiving data to and from the storage units
20
and
48
.
In the above-mentioned composition, in case of writing data from the host A
12
, mirroring modes of three kinds are shown. A first mode is called a synchronous mode, in which data to be stored are stored from the host A
12
through the channel controller
26
into the cache
28
, are stored through the disk controller
30
into the storage unit
20
, are stored through the communication controllers
36
and
42
into the cache
64
, are stored through the disk controller
66
into the storage unit
48
, and after the data storing has been finished, a data completion notice is sent from the data controller
68
to the host A
12
through the communication controllers
42
and
36
and through the channel controller
26
. In this case, the reliability of storing data is high, but since the data completion notice is late, the host A
12
results in being restrained in operation for a long time.
Next, a second mode is called a semi-synchronous mode, in which data to be stored are first sent from the host A
12
to the channel controller
26
together with a write command, and when the cache
28
has received all the data the channel controller
26
sends a write command completion notice to the host A
12
. After this, the data to stored are stored into the storage unit
20
, are stored into the cache
64
through the communication controllers
36
and
42
, and are stored into the storage unit
48
through the disk controller
66
. Then, after the cache
64
has received all the data, the data controller
68
sends a reception response to the data controller
32
through the communication controllers
42
and
36
, and a series of data storing operations are finished. In this semi-synchronous mode, since a completion response is sent to the host A
12
before a data reception response comes from the remote site B, the host A
12
is made faster by a time for processing data transfer and response between the sites than the synchronous mode. From the viewpoint of data reliability, however, there is the possibility of losing data when the data are sent and received between the controllers
16
and
44
.
Next, a third mode is called an adaptive copy (hereinafter, referred to as an adaptive copy) mode, in which data to be stored are first sent from the host A
12
to the channel controller
26
together with a write command, and when the cache
28
has received all the data the channel controller
26
sends a write command completion notice to the host A
12
. The data controller
32
stores a fact that this completion notice has been performed into a queue, and if the next command has been issued from the host A
12
, so long as there is a free space in the storage area of the queue, the data controller
32
sends a completion notice of the said next command to the host A
12
. After this, at a proper timing the data controller
32
stores the data registered at the queue into the storage unit
20
and stores the data into the storage unit
48
through the communication controllers
36
and
42
and through the disk controller
66
. Then, after the data controller
68
has received all the data, it sends a reception response to the data controller
32
through the communication controllers
42
and
36
. Each time the data controller
32
receives the reception response, it decrements the queue, and at the point of time when the queue becomes zero, a series of write operations are completed. In this adaptive copy mode, since a completion response is sent to the host regardless of data transfer with the remote site B so long as there is a free space in the queue, the response is made faster than the second semi-synchronous mode, the semi-synchronous mode. From the viewpoint of data reliability, however, there is the possibility of losing data when a sequence of data corresponding to the number of items registered at the queue are sent and received.
As described above, in the conventional mirroring modes of three kinds, the system operates in a mode fixed by specifying one of these three modes in advance, and for example, in case that the system is set at the synchronous mode, since a command completion notice cannot be sent to the host so long as no reception response comes from the remote site even if the system is heavily loaded, the system can perform a process only in a speed of the same degree as before and this problem makes a bottleneck of the whole system performance.
And in case that a system administrator attempts to change over a mirroring mode to another mirroring mode during a mirroring operation, since it has to issue a specialized command from a maintenance system accompanying a host or disk system and the intervention is performed manually, the system is most heavily loaded and there is the possibility of losing a timing at which a high-speed operation is required.
SUMMARY OF THE INVENTION
The present invention provides a data mirroring method capable of solving the above-mentioned problems, and aims at providing a data mirroring method capable of changing over the mirroring mode among the above-mentioned data mirroring modes of three kinds according to the degrees of burdens on the hosts and the respective controllers.
A data mirroring method of the present invention is a data mirroring method which, in a system provided with a first information processing apparatus composed of a first host and a first disk system for sending and receiving data to and from the first host and a second information processing apparatus composed of a second host and a second disk system, connects the first disk system and the second disk system to each other and makes data common to the first disk system and the second disk system;
said data mirroring method selecting one of data mirroring modes of at least three kinds including a synchronous mode, a semi-synchronous mode and an adaptive copy mode being different in speed of processing the data from one another according to the quantity of operations with the first host.
In a data mirroring method of the present invention, the quantity of operations with the first host is the number of commands received and responded per unit time for sending and receiving data between the first host and the first disk system.
In a data mirroring method of the present invention, the quantity of operations with the first host is the quantity of information received and responded per unit time for sending and receiving data between the first host and the first disk system.
In a data mirroring method of the present invention, the quantity of operations with the first host is related to commands received and responded and commands waiting for being processed out of the commands sent from the first host to the first disk system, and is the sum of valu
Elmore Reba I.
NEC Corporation
Sughrue & Mion, PLLC
LandOfFree
Data mirroring method and information processing system for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data mirroring method and information processing system for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data mirroring method and information processing system for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2997233