JPH04102915A - Direct access storage device - Google Patents

Abstract

PURPOSE:To improve the performance of a cache by allowing this direct access storage device itself to select an optimum value as segment length to be a reference unit for managing the cache by calculating time required for practical I/O. CONSTITUTION:The DASD 1 is provided with a recording medium to be a rotating body, the cache 4, a data correspondence storage means 5 for managing correspondence between the contents stored in the cache 4 and the contents of the recording medium, an I/O time calculating means 6 for calculating time required for I/O based upon the performance value of the DASD 1, and a performance storage means 7 for storing the seaking performance of a head, rotation waiting performance and the performance of data transfer to be executed between the cache 4 and the recording medium after positioning the head on a prescribed sector. The DASD 1 itself determines the segment length so as to improve its performance in accordance with the property of an access from a host computer. Thus, the performance of the DASD 1 can be extracted up to its maximum.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to direct access storage devices.

[Prior Art] Direct access storage devices such as magneto-optical disk devices and fixed magnetic disk devices perform a seek operation to move the head to a track position in a predetermined sector and a seek operation to move the head to a track position in a predetermined sector when recording and reproducing data. Accompanied by the movement of waiting for positioning and rotation. Since these operations are mechanical, they are an obstacle to improving the performance of direct access storage devices.

As one of these measures, the direct access storage device is equipped with a cache using semiconductor memory or the like, and by storing data in this cache, the frequency of access to the recording medium is reduced and speed is increased.

The cache generally has a much smaller capacity than the storage capacity of the recording medium (approximately 1/100 or less of the capacity of a direct access storage device), so it can efficiently manage the data to be accessed and access the necessary data. Various algorithms have been used to improve the time required to do this (hereinafter referred to as input/output time).

In a commonly used method, the cache is managed by virtually partitioning it into fixed lengths. Hereinafter, this unit will be referred to as a segment. A segment is used as a unit for reading from, writing to, and replacing data on a recording medium. The selection of the segment to be replaced is, for example, L
RU (Least Recently Used)
It is carried out based on.

The size of the segment is set to exceed the average data length of a read request from the host computer during production of the direct access storage device, which improves the hit rate and input/output time by reading ahead. We aim to

[Problem to be solved by the invention] However, in the case of random access in which the host computer requests random access (for example, accessing sectors 1000.0 to 100, etc.), it is expected that the input/output time will be shortened by read-ahead. I can't. In addition, increasing the segment length increases the seek distance and the length of data read from the recording medium, which may conversely increase input/output time and degrade performance.

On the other hand, in the case of sequential access in which the data locations to be accessed change sequentially (for example, accessing sectors 0 to 1.2 to 3, etc.), the segment length is larger than the average data length,
and the maximum length, i.e. cache capacity - segment length,
This can reduce input/output time the most.

Furthermore, depending on the access pattern from the host computer, as the segment length increases, the number of times the segment contents are replaced increases, which may lead to an increase in hit rate and input/output time.

Thus, the segment length setting greatly affects the performance of the direct access storage device from the perspective of the host computer. However, although the average data length and the access pattern (sequential or strong access, random access or strong) depend on the operating system and application programs running on the host computer, the segment length is It is common to fix the value to the value at the time of device production.

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for setting the segment length by the direct access storage device itself so as to maximize the performance of the direct access storage device depending on the nature of the access from the host computer.

[Means for Solving the Problems] The direct access storage device of the present invention uses (1) a rotating recording medium, (a) recording/reproducing means for recording and reproducing necessary data, and (b) a host. an interface means for transmitting and receiving control information and data to and from a computer; (c) a high-speed data storage means called a cache for storing data recorded on a recording medium according to a certain algorithm in a semiconductor memory; (d) data (c) data-compatible storage means for managing the correspondence between the contents stored by the high-speed recording means and the contents on the recording medium; (c) an input means for calculating the time required for input/output based on the performance value of the direct access storage device; output time calculation means; (f) seek performance of the head; rotational waiting performance for positioning the head in a predetermined sector after the head reaches a predetermined track; and data high-speed storage means after the head has been positioned in a predetermined sector; The device is characterized by having means for storing performance of data transfer performed between the device and the recording medium.

(2) Using a rotating recording medium, (a) recording/reproducing means for recording and reproducing necessary data; (b) interface means for transmitting and receiving control information and data to and from a host computer; C) A high-speed data storage means called a cache that stores data recorded on a recording medium according to a certain algorithm in a semiconductor memory, etc. (d) Correspondence between the contents stored by the high-speed data storage means and the contents on the recording medium. (e) input/output time calculation means for calculating the time required for input/output based on the performance value of the direct access storage device; (f) time detection means for measuring time; (g) direct access storage device; seek performance measuring means for measuring the seek performance of the storage device using the time detecting means; (h) a rotational wait for determining the time during which the head is positioned in a predetermined sector after the head reaches a predetermined trunk; Performance measuring means: (i) data transfer performance measuring means for measuring the performance of data transfer performed between the data high-speed storage means and the recording medium using the time detection means after the head is positioned in a predetermined sector; It is characterized by having the following.

[Operation] The present invention takes into consideration the seek performance, rotational waiting performance, and data transfer performance of the direct access storage device, and determines the nature of access from the direct access storage device or the connected host computer, thereby efficiently using the cache. You can manage and maximize the performance of your direct access storage devices.

[Example] Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1(a) is a block diagram showing the configuration of a direct access storage device 1 according to the present invention.

FIG. 1(b) is a block diagram showing the configuration of a direct access storage device l according to the present invention.

FIG. 2 is a block diagram showing a flowchart when power is turned on to the direct access storage device 1 according to the present invention.

After the power is turned on, the direct access storage device 1 waits for necessary startup processing and for insertion of the recording medium if the recording medium is replaceable, such as in a magneto-optical disk device (1). Once it is possible to access the recording medium, seek performance measuring means 9, rotation waiting performance measuring means 10. Necessary performance data is acquired by the data transfer performance measuring means 11.

Set the segment lengths for comparing input/output times to sl, s2, etc.
Set as Sn (2). These values are set as candidate segment lengths that are expected to be optimal.

Hereinafter, assuming that these segment lengths S1...Sn are adopted, head positions H1...Hn, number of shift racks, seek time, rotation waiting time, data transfer time T
I...Tn is calculated to calculate the input/output time.

Input/output time T1 calculated corresponding to Sl...Sn
...Set Tn to 0 and initialize it (3).

Head positions H1...Hn corresponding to Sl...Sn
is initialized to the current track position (4). The access count, which stores the number of times the recording medium is actually accessed, is initialized to O (5). Further, the segment length so used in the actual input/output processing is set to 5k (k=1, 2, . . . n), that is, any value selected in the above processing (6). It waits for an access request from the host computer transmitted by the interface means 3 (7).

Note that the input/output time referred to here means the time required to seek to the track where the target sector exists, the time required to position the head in the target sector, and the time required to transfer necessary data between the data high-speed storage means 4 and the recording medium. This is the total time required for transfer between

FIG. 3 is a block diagram showing a flowchart of the seek performance measuring means 9.

The current time is detected by the time detection means 8 (1).

Perform a seek (2). The current time is detected again by the time detection means 8 (3). Calculate the seek time (4). The process ends when the correspondence table between the number of seek tracks and the seek time for calculating the input/output time is completed.

If it is not completed, change the number of tracks to be sought and measure the seek time again (5).

FIG. 4 is a block diagram showing a flowchart of the rotation waiting performance measuring means 10.

The current time is detected by the time detection means 8 (1).

Wait until it is positioned in the target sector (2). The time detection means 8 detects the current time again (3).

Calculate the rotation waiting time (4). Once the rotational wait performance table for calculating input/output time is completed, the process ends.

If it has not finished, change the target sector and measure the rotation waiting time (5).

FIG. 5 is a block diagram showing a flowchart of the data transfer performance measuring means 11.

The current time is detected by the time detection means 8 (1).

The access start sector where the head is already positioned and the number of access sectors are set, and reading from or writing from the recording medium is performed (2). The current time is detected again by the time detection means 8 (3). Find the data transfer time per sector (4).

Once the data transfer performance table for calculating input/output time is completed, the process ends. If it is not completed, change the starting sector and the number of sectors and measure the data transfer performance (5).

FIG. 6 is a block diagram showing a flowchart showing the processing of the direct access storage device when there is a read request.

First, the input/output time calculating means 6 calculates the segment length Sl.
...Input/output time TI assuming that Sn is adopted...
・Calculate Tn.

Next, it is checked by the data correspondence storage means 5 whether or not the data to be read exists in the data high speed storage means 4.

If the data exists in the high-speed storage means 4, the data is transferred to the host computer by the interface means 3 (1
). When some or all sectors to be read do not exist in the data high-speed storage means 4, the recording/reproducing means 2 reads the data segment by segment (2), and the interface means 3 transfers the necessary data to the host computer. Do (3). At this time, the segment length used is S
It is O. Increase the number of accesses by 1 4)
Check whether the number of accesses has reached a predetermined number of times for changing the segment length (5). If the predetermined number of times has been reached, the segment length is changed 6) and the process ends.

In this way, the trigger for changing the segment length is when the number of accesses to the recording medium or the preset number of times (predetermined number of times) is reached. The predetermined number of times is set to a value that is neither too frequent nor too small when changing the segment length.

FIG. 7 is a block diagram showing a flowchart showing the processing of the direct access storage device when there is a write request.

First, the input/output time calculation means 6 calculates the segment length S1.
...Input/output time T1 when assuming Sn is adopted...
・Calculate Tn. A cache that stores data to be written by the host computer using the data-compatible storage means 5.
Decide on the second position.

Next, the interface means 3 transfers data from the host computer to the data high-speed storage means 4 to the cache (1). At this time, data is also written to the recording medium by the recording/reproducing means 2 (2). The number of accesses is counted up by one (3), and it is checked whether the number of accesses has reached the predetermined number of times for changing the segment length (4). If the predetermined number of times has been reached, the segment length is changed (5) and the process ends.

FIG. 8 is a block diagram showing the flowchart of the input/output time calculation means 6. l, which identifies the set segment length, is set to 1 (1).

The difference between nt (the current head position assuming that the segment length Si is adopted) and the track to be sought is calculated (2). Set Hi as the track to be sought (3).

The time required for seeking is obtained from the seek performance measurement means 9 or the performance storage means 7 (4).

The rotation wait time is obtained from the rotation wait performance measurement means 10 or the performance storage means 7 (5). The data transfer time is obtained from the data transfer performance means 11 or the performance storage means 7 (6). T
Add the seek time, rotation waiting time, and data transfer time to i (7). Add 1 to i (8). When all set segment lengths have been calculated and the calculation has been completed, the calculation is ended (9).

FIG. 9 is a block diagram showing flowchart I. of changing the segment length.

Input/output time T1 corresponding to segment length S1...Sn
...Choose the minimum Tk from Tn (1).

The segment length SO used for subsequent processing is set to Sk (2). Initialize T1...Tn to O in order to recalculate the input/output time associated with subsequent access processing (3)
. Hl... Set I-1n to the value of the track where Sodo currently exists (4). Also, the number of accesses is initialized to 0 (5).

When the segment length is changed, the seek stored in the data high-speed storage means 4 based on the segment length before the change is replaced or written by the previous segment length.

As mentioned above, in this embodiment, since it is assumed that the performance differs depending on the position of the accessed sector such as CLV and ZCAV, it is assumed that a performance table is created, or if the average value is used. It is not necessarily necessary to create a performance table.

Furthermore, if the performance of the direct access storage device 1 is stored in the performance storage means 7 when the direct access storage device 1 is produced, there is no need to use each performance measuring means.

Furthermore, in this embodiment, when writing a seek, w
N to r it e-t h r o u g h method
However, it goes without saying that the write-back method can also be applied in the same way as this embodiment.

[Effects of the Invention] As described above, according to the present invention, the segment length, which is the basic unit in which the direct access storage device itself manages the cache, can be optimized by calculating the time actually required for input/output. Select. Therefore, if only the selectable segment lengths are set during direct access storage device production,
Even when connected to a host computer running various operating systems and application programs,
This allows you to maximize the performance improvement effect of caching.

[Brief explanation of drawings]

FIG. 1(a) is a block diagram showing the configuration of a direct access storage device according to the present invention. FIG. 1(b) is a block diagram showing the configuration of a direct access storage device according to the present invention. FIG. 2 is a diagram showing a flowchart when the direct access storage device according to the present invention is powered on. FIG. 3 is a flowchart for measuring the seek performance of a direct access storage device according to the present invention. FIG. 4 is a flowchart for measuring rotational wait performance of a direct access storage device according to the present invention. FIG. 5 is a flowchart for measuring data transfer performance of a direct access storage device according to the present invention. FIG. 6 is a flowchart showing the processing of a read request to a direct access storage device according to the present invention. FIG. 7 is a flowchart showing the processing of a write request to a direct access storage device according to the present invention. FIG. 8 is a diagram showing a flowchart of input/output time calculation in the present invention. FIG. 9 is a diagram showing a flowchart of changing the segment length in the present invention.・Direct access storage device ・Recording/playback means ・Interface means ・Data high-speed storage means ・Data correspondence storage means ・Input/output time calculation means ・Performance storage means Time detection means Seeking performance measuring means Rotation waiting performance measuring means Data transfer performance measuring means Up

Claims (2)

[Claims] (1) In a direct access storage device using a rotating recording medium, (a) recording/reproducing means for recording and reproducing necessary data; (b) an interface for transmitting and receiving control information and data to and from a host computer. (c) high-speed data storage means called a cache that stores data recorded on a recording medium according to a certain algorithm in a semiconductor memory or the like; (d) contents stored by the high-speed data storage means and contents on the recording medium; (e) I/O time calculation means that calculates the time required for input/output based on the performance value of the direct access storage device; (f) Seek performance of the head; and means for storing performance of data transfer between the data high-speed storage means and the recording medium after the head is positioned at the predetermined sector. A direct access storage device characterized by: (2) In a direct access storage device using a rotating recording medium, (a) recording/reproducing means for recording and reproducing necessary data; (b) an interface for transmitting and receiving control information and data to and from a host computer; (c) high-speed data storage means called a cache that stores data recorded on a recording medium according to a certain algorithm in a semiconductor memory or the like; (d) contents stored by the high-speed data storage means and contents on the recording medium; (e) input/output time calculation means for calculating the time required for input/output based on the performance value of the direct access storage device; (f) time detection means for measuring time; (g) ) seek performance measurement means for measuring the seek performance of the direct access storage device using the time detection means; (h) rotational wait for measuring the time during which the head is positioned in a predetermined sector after the head reaches a predetermined track; Performance measuring means: (i) data transfer performance measuring means for measuring the performance of data transfer between the data high-speed storage means and the recording medium using the time detection means after the head is positioned in a predetermined sector; A direct access storage device comprising: