JPS62241022A - Method for controlling medium exchange of cluster type input and output device - Google Patents

Abstract

PURPOSE:To decrease the medium exchanging frequency and to shorten the turn-around time by adding the weight to a counter with an access given to one's own medium and then giving '-1' to the counter with an access given to another medium to perform the exchange control according to the counter value. CONSTITUTION:When an input/output request is given to a medium (i), the control information on all drive mechanisms are checked and the weight alphai is added to the access count value Ai if the medium (i) is already set. Then '1' is subtracted from the access values of all drive mechanisms excluding this relevant mechanism (i). While a drive mechanism (j) having the minimum access count value is detected in case the medium (i) is not set yet. Then a medium (j) set to the mechanism (j) is replaced with the medium (i) by an automatic medium exchange mechanism. The access count value is initialized after exchange of said medium and furthermore the identifying information the medium (i) and the weight alphai are registered to the control information. Then the desired input/output processing is carried out after the medium (i) is set and the control information is replaced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises 1. The present invention relates to a computer system including a collective input/output device having a plurality of drive mechanisms and an automatic medium exchange mechanism, and particularly relates to an automatic medium exchange control method that takes into account the frequency of access to the medium.

[Conventional technology]

A conventional automatic medium exchange control method that focuses on the access frequency of the medium is LFU (Least Frequent).
There is a control method using the ntlyUsed ) algorithm.

In this LFU method, all the media are set in multiple drive mechanisms, and there is no free space.

When a request to set a new medium is issued, the medium accessed least frequently is removed and a new medium is sected.

Access frequency is expressed by the number of accesses over a certain period of time.

A specific example will be explained with reference to FIG.

First, access count value Aj (1<j<n)
'rSet for each drive. Access count value A
, is counted up each time an input/output request is issued to the medium set in that drive mechanism. With all media set in n drive mechanisms,
When a request to set a new medium m is issued, the medium set in the drive mechanism 1 with the minimum access count f1^Aj at that time is removed, and a new medium m is set.

[Problem that the invention seeks to solve]

In the conventional LFU method, access frequency is managed by the number of accesses to a medium within a certain period of time, so if there is a local bias in time, two media that should not be removed are removed, and conversely, unnecessary media are removed. There is a disadvantage that the medium remains without being removed.

Concrete example? This will be explained with reference to FIG.

Pay attention to medium 2 set in drive 2 and medium i set in drive i. Medium 2 was accessed four times in the first half of a certain period until a request to set a new medium m was issued. On the other hand, medium i was accessed three times in the latter half of the certain period. In this case, it is considered that medium 2 is used in the first half of the nine periods and is unnecessary in the second half, whereas medium i is used in the second half and is accessed continuously thereafter. However, the access count value A
When compared with j, the value Ai of medium l is the minimum, so
It will be removed in order to set a new medium mf.

Then, when there is a secondary access to medium i, the medium exchange process is executed again, slowing down the input/output process.

Generally, in collective input/output devices, it is important to eliminate the number of media exchanges in order to shorten turnaround time and improve overall system throughput.

An object of the present invention is to provide a control method that reduces the number of medium exchanges.

[Means for solving problems]

The automatic medium exchange control method of the present invention includes, for each drive mechanism, "identification information" used when the control software of the host device recognizes the medium set in the drive mechanism, and the access frequency of the medium. When accessing a medium that has control information consisting of an "access count value" and a "weight" that is added to the access count value for each access, the control software of the host device has already been set.

The weight specified in the control information is added to the access count value, and the access count values of all other drive mechanisms other than the drive mechanism are subtracted by 1#.
Also, when the control software of the host device accesses a medium that has not been sected.

Find the minimum access count value for all drive mechanisms,
After removing the medium set in the drive mechanism using the automatic medium exchange mechanism and replacing the medium, the access count value of the drive mechanism is initialized and the identification information and weight of the newly set medium are transferred to the control information. , and the access count values of all other drive mechanisms are decremented by "1".

〔Example〕

Next, details of an embodiment of the automatic medium exchange control method of the present invention will be explained with reference to the drawings.

(1) Configuration FIG. 1 and FIG. 2 each illustrate an embodiment of the present invention.

In FIG. 1, a plurality of (,) drive mechanisms 220 to 22 are shown.
3. A plurality of (e) media 240 to 243. Automatic media exchange mechanism 230 for setting or removing media from the drive mechanism. and a collective input/output device 200 that incorporates a control unit 210 that incorporates media exchange processing differences and control information that controls an automatic media exchange mechanism, and a host device 100 that incorporates control software 110 that controls the collective input/output device. It is composed of.

In FIG. 2, a plurality (n) of drive mechanisms 220 to 22 are shown.
3. plural) media 240-243. and a collective input/output device 200 incorporating an automatic medium exchange mechanism 230, and control software 11 that incorporates media exchange processing and control information to control the automatic medium exchange mechanism and controls the collective input/output device.
◎ The difference between the embodiments shown in FIGS. 1 and 2 is that the automatic media exchange mechanism 2
It is located at the location of the media exchange processing and control information that controls 301. The former exists on the collective input/output device 200 side, and is usually the firmware of the control unit.

Realize that function. The latter exists on the host device 100 side, and usually realizes its functions with software (operating system or computer program).

(n) Operation The operation of the present invention will be explained in detail with reference to FIG.

When an input/output request to medium i is issued from the control software of the host device, it is checked whether medium 1 has already been set by referring to the control information of all drive mechanisms (
Processing 301).

If medium l has already been set in drive mechanism i, weight αi is added to its access count value Ai (
Process 302).

Next, the access count values of all drive mechanisms other than the relevant drive mechanism 1 are decreased by '1''.

If the access count value becomes a negative value by decreasing @l, it is set as OJ' (process 303).

If the medium i for which the input/output request has been issued is not set, the drive mechanism j having the minimum value among all the access count values is determined (process 304).

Next, the medium j set in the drive mechanism j is exchanged with the medium 1 using the fully automatic medium exchange mechanism (process 30
5).

After replacing the medium, the access count value is initialized. Specifically, initial values specified in advance for each system are set. Furthermore, the identification information of medium i and the weight α
i is registered in the control information (process 306).

Next, process 302. Process 303t - Execute.

After setting the medium i and updating the control information, the requested input/output process is executed (process 307).

This will be explained in detail in Figure 4. Assume that the process is started with all media set in n drive mechanisms @In this case, all access count values Ai (l<i<n) is initially set to "0". Next, when you access medium i2,
A weight α,=5 is added to the access count value AI of the medium 1. At this time, another access count value AJ (2<
If "1" is subtracted from "j<n", everything becomes 1-1", so it is set as "0#".

When the medium 2 is accessed next, a weight α2,055 is added to the access count value A2 of the medium 2. Then, set the other access count value Aj (j=l, a<jrin) as @1#
reduce However, from A3 to An is -1", so @0
Set to 1.

Subtract.

Next, when a request to access medium m that is not set is issued, the drive mechanism having the minimum access count value at that time is found. In this example, the minimum value is A
Since 3=0, the medium 3 set in the drive mechanism 3 is removed using the automatic medium exchange mechanism 230, and the medium m is set in the replacement tray.

In the example of FIG. 4, the weight αi added to the access count value is set to the same value (=5) for all media, but
It is also possible to set different values for each medium.

For example, in the example of FIG. 5, weight α1=5. α2=5゜α3
=20t..., α1=io,..., α. =5.

In this case, even if the access is made at exactly the same timing as in the example of FIG. 4, the medium that is ultimately replaced with medium m is 9 medium 1, which is different from the example of FIG. In this way, a large value is set for the weight αi for a medium that needs to be set at all times even if the access frequency is low.

The specific effects will be explained with reference to FIG.

In the example of FIG. 6, the medium is accessed at exactly the same timing as in FIG. 8, which is an example of the prior art. In the conventional method, when there is a request to set medium m, medium i with the minimum access count value (Ai = 3) at that time is removed, but in the method of the present invention, the minimum access count value A2 = 0. Therefore, medium 2 is removed. In this example, it is considered appropriate to remove medium 2 and sect a new medium m.

〔Effect of the invention〕

As explained above, the present invention takes into consideration the relationship between the access frequency and the number of accesses to other media.

When accessing the own medium, the weight is added to the access counter, and when accessing another medium, the access counter is subtracted by 11". By controlling medium exchange using this access count value, unnecessary medium exchange is avoided. Reduce the number of times
This has the effect of shortening turnaround time.

[Brief explanation of drawings]

1 and 2 are block diagrams showing embodiments of the present invention, FIG. 3 is a flowchart of automatic medium exchange control processing, and FIGS. 4, 5, and 6 show specific operations of the present invention. Figures 7 and 8 show the specific operations of the conventional method. , is a chart. In FIGS. 1 and 2, 10...media exchange processing. 20... Control information, 100... Upper device, 11o.
・・Control unit, 200 ・・Collective type input/output device, 2
10... Control unit, 220-223... Drive mechanism, 23°... Automatic medium exchange mechanism, 240-243...
・Medium. (C), 9 tsubo (1h)

Claims (1)

[Claims] 1. In a computer system that includes a collective input/output device with multiple drive mechanisms and an automatic medium exchange mechanism, "identification information" of the medium set for each drive mechanism and "identification information" indicating the access frequency of the medium are set for each drive mechanism. Access count value”
and a "weight" that is added to the access count value each time the access is made. When accessing a medium for which the control software of the host device has already been set, the control information is added to the access count value. Adds the weight specified in , and subtracts "1" from the access count values of all drive mechanisms other than the one in question, and also when accessing a medium for which the control software of the host device is not set. calculates the minimum access count value of all drive mechanisms, removes the medium set in that drive mechanism using the automatic medium exchange mechanism, and
After replacing the medium, initialize the access count value of the drive mechanism in question, register the identification information and weight of the newly set medium in the control information, and decrement the access count values of all other drive mechanisms by "1". A media exchange control method for collective input/output devices featuring features.