JP3781358B2 - External storage controller and data transfer method between external storage controllers - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an external storage subsystem that stores data by a write command from a host device, and more particularly to an external storage subsystem that transfers the same data to another external storage subsystem.
[0002]
[Prior art]
When data used in a host device is held in a plurality of external storage devices, primary and secondary external storage devices that hold the same data may be provided under different external storage control devices. In this case, when these external storage control devices are connected and a write command is received by the external storage control device that controls the primary external storage device, the primary external storage control device controls the secondary external storage device. By issuing this write command to the control device, the data in the primary and secondary external storage devices are matched.
[0003]
In US Pat. No. 5,155,845, an external storage control device that controls a primary external storage device and an external storage control device that controls a secondary external storage device are connected, and a primary external device that has received a write command from a host device. It is described that the storage control device performs data transfer to the secondary external storage control device and performs write processing to the primary / secondary external storage device in parallel.
[0004]
[Problems to be solved by the invention]
When the data in the external storage device is regarded by the host device as being in the CKD (count, key, data) format used in the large computer system, a channel command instructing the data transfer for each individual record is consecutive. Issued.
[0005]
Here, consider a case where a plurality of records are continuously written in one command chain. In an external storage subsystem having primary and secondary external storage devices that hold the same data under different external storage control devices, R1, R2 and disk devices that are primary storage control devices from the channel device that is the host device When a command chain (DEFINE EXTENTENT / LOCATE RECORD / WRITE (R1) / WRITE (R2) / WRITE (R3)) for writing three consecutive records of R3 is issued, the channel device and the primary disk control device, and In the exchange of data with the primary disk control device, a command chain is generated several times between the primary and secondary disk control devices every time data of the write record is transferred, as in the processing sequence of FIG.
[0006]
Further, when data is duplicated using such a system configuration, the distance between the primary and secondary external storage control devices increases from the viewpoint of switching to a backup system in the event of a disaster, and an optical fiber is used for the interface. For this reason, the command chaining time, which is considered to be almost fixed for metal cables, is in a state where the influence of the cable length of the interface cannot be ignored. Furthermore, since the above-described data duplication is a backup function, it is necessary to minimize the influence on the normal processing by the writing processing to the secondary external storage control device.
[0007]
However, when multiple writes are executed in one command chain as described above, the number of command chains between the primary external storage control device and the secondary external storage control device increases, so that the secondary external storage control The command chaining time required for the writing process to the device cannot be ignored, and the backup process may greatly increase the throughput of the normal process.
[0008]
The object of the present invention is to optimize the write processing time to the secondary external storage control device in consideration of the command chaining time between the primary and secondary external storage control devices, thereby achieving the original purpose even in the above-described situation. It is to provide means that can.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an external storage control device according to the present invention is connected to a plurality of first external storage devices and controls data transfer between the first external storage device and a host device. A memory means connected to another external storage control device having a plurality of second external storage devices, wherein a plurality of write data is continuously stored by a write command from the host device; and the memory means Means for transferring the plurality of write data stored in the first external storage device to the other external storage control device, wherein the same data is stored in the first external storage device and the second external storage device. In this case, when the write command for the data in the first external storage device is received from the host device, the plurality of write data received by the write command are stored in the other external storage. Rather than transferring to the control device as it is, it is better to transfer a plurality of write records including the plurality of write data received by the write command to the other external storage control device as one or a plurality of tracks. When the transfer processing time is early, the plurality of write records are collectively transferred to the other external storage control device, and when the transfer processing time is slow, the plurality of write data received by the write command is directly used. After transferring and receiving a status report for the write command from the other external storage control device, the status report is transmitted to the host device.
Predict the command chaining time between the primary and secondary external storage control devices, and start the write processing to the secondary external storage control device before starting the write processing to the secondary external storage control device and the secondary external storage from the command issued to the primary external storage control device The processing time for writing to the control device can be predicted . Also, compare the predicted processing time and the data processing time when the data for the write record or the data for one or more tracks including the write record is transferred at once with the dedicated command to the secondary external storage controller and to select an optimum command chain with respect Fukugaibu storage controller having instructions for writing together the data.
A storage system according to the present invention is an external storage control device that is connected to a plurality of first external storage devices and controls data transfer between the first external storage device and a host device, and a plurality of second external storage devices A memory means connected to another external storage control device having a storage device, wherein a plurality of write data is continuously stored by a write command from the host device, and the plurality of write data stored in the memory means Means for transferring to the other external storage control device, and when the same data is stored in the first external storage device and the second external storage device, When the write command for the data in the external storage device is received, the plurality of write data received by the write command is transferred as it is to the other external storage control device If it is faster to transfer a plurality of write records including the plurality of write data received by the write command to the other external storage control device as one or a plurality of tracks, The plurality of write records are collectively transferred to the other external storage control device, and when the transfer processing time is slow, the plurality of write data received by the write command are transferred as they are, and the other external storage After receiving a status report for the write command from the control device, the status report is transmitted to the host device.
Predict the command chaining time between the primary and secondary external storage control devices, and start the write processing to the secondary external storage control device before starting the write processing to the secondary external storage control device and the secondary external storage from the command issued to the primary external storage control device The processing time for writing to the control device can be predicted. Also, compare the predicted processing time and the data processing time when the data for the write record or the data for one or more tracks including the write record is transferred at once with the dedicated command to the secondary external storage controller And an instruction for selecting an optimum command chain for the secondary external storage control device and writing the data together.
[0010]
The above command chaining time is a means for measuring the command chaining time from a specific command issued between the primary and secondary external storage control devices to the next command, or the interface cable length between the primary and secondary external storage control devices from the outside in advance. This is realized by means for setting and calculating the command chaining time from this interface cable length.
[0011]
On the other hand, the write processing time to the secondary external storage control device can be calculated from the above information and command information issued to the primary external storage control device. That is, a command chain used for data input / output includes specific and at least two channel commands before a command for starting data transfer. For example, in the case of an external storage control device, the DEFINE EXTENT command and the LOCATE RECORD command are issued before data transfer, and the number of processing records and the data length are given by the LOCATE RECORD command. It is possible to calculate the transfer amount.
[0012]
Further, the command chaining time between the primary and secondary external storage control devices depends on the interface cable length and the processing capability of the external storage control device, but hardly depends on the commands before and after the command chaining. Therefore, the command chaining time during data transfer can be predicted by measuring two command chaining times. Note that when installing a backup system, the interface cable length between the primary and secondary external storage control devices and the support function of the external storage control device are already known, and this information is set in the primary external storage control device when the system is installed. The command chaining time can also be predicted from the set interface cable length.
[0013]
If the command chaining time can be predicted, the processing time when the command chain from the channel is issued to the secondary external storage control device can be predicted from the data transfer amount. Or, compare the processing time when the data for one or more tracks including the write record is written at once with the command to write it together, and issue the optimal command chain to the external storage controller on the secondary side can do.
[0014]
In addition, the external storage control device according to the present invention transfers the data to the external storage control device that receives the write command from the data buffer in the external storage control device in response to the write command. Means for confirming the presence in the data buffer of the control device, and means for transferring the data. Furthermore, the transfer processing time can be further shortened by transferring the physical data in the data buffer including the control byte and the check byte together in the data transfer.
[0015]
In addition, when the read target data from the host device exists in the external storage controller buffer of the external storage device other than the external storage controller that received the read command in response to the read command from the host device, this data Is transferred to the external storage control device that has received the read command by the above transfer method, so that the read processing time can be shortened without accessing the external storage device.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a configuration diagram of a data processing system according to an embodiment of the present invention. This data processing system includes a main storage device 1, a channel device 2, a main storage device 6 that is a backup system, and a channel device 7. Further, a primary disk control device 3 having a buffer memory 4, a primary disk device 5, and a secondary disk control device 8 and a secondary disk device 10 incorporating a buffer memory 9 are included. The channel device 2 and the primary disk control device 3 are connected by an interface cable 11, and the primary disk control device 3 and the secondary disk control device 8 are connected by an interface cable 12.
[0017]
As shown in FIG. 2, in addition to the buffer memory 4, the primary disk control device 3 includes a channel command analysis unit 31, a secondary disk control device issue command determination unit 32, a secondary disk control device management information table 33, a timer 34, and a secondary disk. It comprises a control device command issuing unit 35 and a cable length / secondary disk control device function determining unit 36. Reference numerals 31 to 33 and 35 to 36 denote functional blocks realized by a microprogram executed by a microprocessor built in the disk control device 3. The timer 34 is a hardware counter that is counted up at a constant period. The secondary disk control device 8 has the same configuration.
[0018]
In the primary disk controller 3, the timer 34, the secondary disk controller command issuing unit 35, and the cable length / secondary disk controller function determining unit 36 measure the command chaining time between the primary and secondary disk controllers. Then, the command chaining time Tsg measured by the timer 34 at the time of command processing issued when the primary / secondary disk device pair is established is stored in the management table 33 in the primary disk control device.
[0019]
Further, the primary disk control device acquires the support function level of the secondary disk control device when the primary / secondary disk device pair is established, and similarly stores it in the management table 33 in the primary disk control device. Whether this information can receive a command to write data for the write record or data for one or more tracks including the write record to the secondary disk controller when a write command is issued to the secondary disk controller later. Used to determine whether or not.
[0020]
If the secondary disk control device issue command determination unit 32 determines that the dedicated command cannot be received based on the support function level information, when the write command is received from the channel device 2, the secondary disk control device command issue unit 35 unconditionally. A command chain from the channel device is issued to the secondary disk control device. Therefore, it is possible to connect to a conventional model that does not support this function.
[0021]
When a write command is issued from the channel device 2 to the primary disk control device 3, the channel command analysis unit 31 determines whether this write command is for a disk device forming a primary / secondary pair.
[0022]
If it is for the primary / secondary pair forming disk device, the information from the secondary disk control device management information table 33, the number of transfer records N of the LOCATE command analyzed by the channel command analysis unit 31, and the average record length L are used. Then, a comparison graph is created when the received command chain is directly issued from the channel device to the secondary disk control device and when one track including the write record is transferred together (see FIG. 6). Here, the straight line I can be expressed by the following equation from the command chaining time Tsg between the primary and secondary disk control devices, the analysis value, and the data transfer speed V between the primary and secondary disk control devices 3 and 8 that have become known.
[0023]
Ts = NL / V + (N−1) Tsg
A straight line II represents the transfer time Ts ′ (a constant value) when the record length Na for one track of the record length L is transferred together.
[0024]
Ts ′ = NaL / V + Tsg
The secondary disk controller issued command determination unit 32 issues the command chain received from the channel device to the secondary disk controller from the comparison graph and the number N of records transferred in the command chain as it is, or collects one track. Determine whether to transfer.
[0025]
Assuming the case of writing 6 records to the 8 records / track track shown in FIGS. 4, 5 and 6, the graph shows the number of records including the contacts of the straight lines I and II (4 records) as one boundary. If the data is transferred together, it can be predicted that the processing time can be shortened by reducing the number of command chains.
[0026]
The secondary disk controller command issuing unit 35 issues an optimized command chain to the secondary disk controller 8 in accordance with the instruction from the secondary disk controller issued command determination unit 32.
[0027]
【The invention's effect】
According to the present invention, in the data transfer process between the primary disk controller and the secondary disk controller, the command chain received from the channel device is issued to the secondary disk controller as it is, Data or data for one or a plurality of tracks including a write record is compared with a case where the data is transferred at a time by a command to write it together, and is issued to the secondary disk controller so that the processing time is minimized. By selecting the command chain, it is possible to minimize the time required for writing to the secondary disk device as backup processing.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a data processing system in an embodiment of the present invention.
FIG. 2 is an internal configuration diagram of a disk control device according to an embodiment of the present invention.
FIG. 3 is a diagram showing data exchange between a channel device, a primary disk control device, and a secondary disk control device, which are host devices.
FIG. 4 is a diagram showing a case where data transfer is performed between primary and secondary disk controllers in units of tracks in the embodiment of the present invention.
FIG. 5 is a diagram showing data of 8 records / 1 track stored in a data buffer in the disk controller according to the embodiment of the present invention.
FIG. 6 is a diagram showing the relationship between the number of transfer records and the processing time in the embodiment of the present invention.
[Explanation of symbols]
3 Primary disk control device 8 Secondary disk control device 12 Interface cable between primary and secondary disk control devices 32 Secondary disk control device issue command determination unit 33 Secondary disk control device management information table 34 Timer 35 Secondary disk control information command issue unit 36 Cable length / secondary Disk controller function judgment unit

Claims (4)

An external storage control device connected to a plurality of first external storage devices and controlling data transfer between the first external storage device and a host device,
Memory means connected to the other external storage controller having a plurality of second external storage device, a plurality of write data by write instruction from the host device is stored continuously,
Means for transferring the plurality of write data stored in the memory means to the other external storage control device;
With
If said first external storage device and said second external storage device and the same data is stored, when the from the upper apparatus receives the write command to data in the first external storage device,
Rather than directly transferring the plurality of write data received by the write command to the other external storage control device, a plurality of write records including the plurality of write data received by the write command are transferred to one or a plurality of tracks. If the transfer processing time is faster when transferring to the other external storage control device as a whole, the plurality of write records are transferred to the other external storage control device collectively and the transfer processing time is slower. In this case, the plurality of write data received by the write command are transferred as they are,
After receiving a status report for the write command from the other external storage control device, the status report is transmitted to the host device. The external storage control device according to claim 1.
Write data stored in the memory means is written to the external storage device. An external storage control device connected to a plurality of first external storage devices and controlling data transfer between the first external storage device and a host device,
Memory means connected to the other external storage controller having a plurality of second external storage device, a plurality of write data by write instruction from the host device is stored continuously,
Means for transferring the plurality of write data stored in the memory means to the other external storage control device;
With
If said first external storage device and said second external storage device and the same data is stored, when the from the upper apparatus receives the write command to data in the first external storage device,
Rather than directly transferring the plurality of write data received by the write command to the other external storage control device, a plurality of write records including the plurality of write data received by the write command are transferred to one or a plurality of tracks. If the transfer processing time is faster when transferring to the other external storage control device as a whole, the plurality of write records are transferred to the other external storage control device collectively and the transfer processing time is slower. In this case, the plurality of write data received by the write command are transferred as they are,
After receiving a status report for the write command from the other external storage control device, a status report is transmitted to the host device. The storage system of claim 3.
Write data stored in the memory means is written to the external storage device.

Images