CN112000487B - Scrub pressure adjusting method, device and medium - Google Patents

Abstract

The embodiment of the present invention discloses a method, device and medium for adjusting the scrub pressure, which acquires the process pressure of the cluster; triggers the scrub state machine according to the process pressure of the cluster and the execution conditions of the scrub task, and the system automatically adds the scrub task at this time. Lock operation, in order to reduce the time taken by this lock operation, you can adjust the number of objects in the scrub task to perform this scan task according to the process pressure of the cluster; perform this scan task according to the number of objects. Each time a scan task is completed, the number of objects in the scrub task to perform the scan task is adjusted according to the process pressure of the cluster, and the operation ends when all the scan tasks included in the scrub task are completed. According to the process pressure, the number of objects to be scanned is automatically adjusted, which effectively reduces the impact of the scrub task on the front-end business.

Description

A kind of scrub pressure adjustment method, device and medium

technical field

The present invention relates to the technical field of distributed storage, and in particular, to a scrub pressure adjustment method, device and computer-readable storage medium.

Background technique

For distributed storage clusters, data consistency between replicas needs to be guaranteed. During the operation of the cluster, data inconsistency between replicas may occur due to various reasons. Data consistency check (scrub) provides us with a mechanism to perceive data inconsistency between replicas. Scrub will scan the data between replicas. Compare, and it will show up when data inconsistency is found.

The scrub operation needs to be processed by adding pg locks, and the execution of the front-end business of the cluster also needs to add pg locks. Due to the relationship between the pg locks, the scrub operation and the front-end business are mutually exclusive operations. When there are a large number of scrub triggers , which will seriously affect the front-end services of the cluster.

It can be seen that how to reduce the impact of the scrub task on the front-end business is a problem that needs to be solved by those skilled in the art.

SUMMARY OF THE INVENTION

The purpose of the embodiments of the present invention is to provide a scrub pressure adjustment method, device and computer-readable storage medium, which can reduce the impact of scrub tasks on front-end services.

To solve the above technical problems, an embodiment of the present invention provides a scrub pressure adjustment method, including:

Get the process pressure of the cluster;

Trigger the scrub state machine according to the process pressure of the cluster and the execution conditions of the scrub task;

According to the process pressure of the cluster, adjust the number of objects in the scrub task to perform this scan task;

Execute this scan task according to the number of objects, and adjust the number of objects to perform this scan task in the scrub task according to the process pressure of the cluster each time a scan task is completed, until all the objects included in the scrub task are When all the scanning tasks are completed, the operation ends.

Optionally, the triggering of the scrub state machine according to the process pressure of the cluster and the execution conditions of the scrub task includes:

When the PG is in the task execution state and the current time satisfies the execution time of the scrub task, determine whether the process pressure of the cluster belongs to the preset high pressure range;

When the process pressure of the cluster does not belong to the preset high pressure range, the scrub state machine is triggered;

When the process pressure of the cluster falls within the preset high pressure range, the scrub state machine is triggered when the scrub task reaches the deadline.

Optionally, after performing this scan task according to the number of objects, it also includes:

Determine whether the process pressure of the cluster belongs to a preset high pressure range;

When the process pressure of the cluster falls within the preset high pressure range, wait for a preset time before executing the step of adjusting the number of objects in the scrub task to perform the scan task according to the process pressure of the cluster .

Optionally, according to the process pressure of the cluster, adjusting the number of objects in the scrub task to perform this scan task includes:

Find the number of objects matching the process pressure of the cluster from the pre-established correspondence list, and use the number of objects as the number of objects in the scrub task to perform this scan task; wherein, the The correspondence list records the correspondence between different process pressure ranges and the number of objects.

Optionally, after performing this scan task according to the number of objects, it also includes:

Determine whether the object data obtained by executing this scan task is consistent with the object data fed back by the standby device;

When the object data obtained by executing the current scan task is inconsistent with the object data fed back by the standby device, the scrub task is marked as an error state.

The embodiment of the present invention also provides a scrub pressure adjustment device, including an acquisition unit, a trigger unit, an adjustment unit and an execution unit;

The obtaining unit is used to obtain the process pressure of the cluster;

The triggering unit is used to trigger the scrub state machine according to the process pressure of the cluster and the execution conditions of the scrub task;

The adjustment unit is configured to adjust the number of objects in the scrub task to perform this scan task according to the process pressure of the cluster;

The execution unit is configured to perform the scan task according to the number of objects, and adjust the number of objects in the scrub task to perform the scan task according to the process pressure of the cluster each time a scan task is completed, until the scan task is completed. When all the scanning tasks included in the scrub task are completed, the operation ends.

Optionally, the triggering unit includes a judging subunit, an executing subunit and a waiting subunit;

The judging subunit is used to judge whether the process pressure of the cluster belongs to the preset high pressure range when the PG is in the task execution state and the current time meets the execution time of the scrub task;

The execution subunit is used to trigger the scrub state machine when the process pressure of the cluster does not belong to the preset high pressure range;

The waiting subunit is configured to trigger the scrub state machine when the process pressure of the cluster belongs to a preset high pressure range and wait for the scrub task to reach the deadline.

Optionally also includes a pressure judging unit and a waiting unit;

the pressure judgment unit, configured to judge whether the process pressure of the cluster belongs to a preset high pressure range;

The waiting unit is configured to, when the process pressure of the cluster belongs to a preset high pressure range, wait for a preset time before executing the scan according to the process pressure of the cluster and adjusting the scrub task to execute this scan The number of steps for the number of objects in the task.

Optionally, the adjustment unit is specifically configured to find the number of objects matching the process pressure of the cluster from a pre-established correspondence list, and use the number of objects as the number of objects in the scrub task to execute this time. The number of objects of the scanning task; wherein, the correspondence list records the correspondence between different process pressure ranges and the number of objects.

Optionally, also include a data judging unit and a marking unit;

The data judging unit is used for judging whether the object data obtained by executing this scanning task is consistent with the object data fed back by the standby device;

The marking unit is configured to mark the scrub task as an error state when the object data obtained by executing the current scan task is inconsistent with the object data fed back by the standby device.

The embodiment of the present invention also provides a scrub pressure adjustment device, including:

memory for storing computer programs;

The processor is configured to execute the computer program to implement the steps of the scrub pressure adjustment method according to any one of the above.

An embodiment of the present invention further provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the method for adjusting the scrub pressure according to any one of the above-mentioned methods is implemented. step.

It can be seen from the above technical solutions that the process pressure of the cluster is obtained; the scrub state machine is triggered according to the process pressure of the cluster and the execution conditions of the scrub task. After the scrub state machine is triggered, the system automatically locks the scrub task. In order to reduce the time occupied by this locking operation, you can adjust the number of objects in the scrub task to perform this scan task according to the process pressure of the cluster; perform this scan task according to the number of objects. The number of objects to be scanned in a scrub task is often large. Generally, multiple scan tasks need to be performed. Therefore, each time a scan task is completed, the number of objects to be scanned in the scrub task can be adjusted according to the process pressure of the cluster. , until all the scan tasks included in the scrub task are completed, the operation ends. In this technical solution, the number of objects to be scanned by the current scrub task can be automatically adjusted according to the process pressure of the cluster. Under the condition that the scrub task can be executed smoothly, the time that the scrub task occupies the pg lock can be effectively reduced, so that the Effectively reduce the impact of scrub tasks on front-end business.

Description of drawings

In order to explain the embodiments of the present invention more clearly, the following will briefly introduce the accompanying drawings that need to be used in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention, which are not relevant to ordinary skills in the art. As far as personnel are concerned, other drawings can also be obtained from these drawings on the premise of no creative work.

FIG. 1 is a flowchart of a method for adjusting scrub pressure according to an embodiment of the present invention;

2 is a schematic structural diagram of a scrub pressure adjustment device provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of a hardware structure of a scrub pressure adjusting device according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

In order to make those skilled in the art better understand the solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

Next, a scrub pressure adjustment method provided by an embodiment of the present invention is described in detail. FIG. 1 is a flowchart of a method for adjusting scrub pressure according to an embodiment of the present invention, and the method includes:

S101: Obtain the process pressure of the cluster.

After an Object-based Storage Device (OSD) is started, a scrub task is registered for each Placement Group (PG).

The process pressure of the cluster can include CPU usage and disk usage. In this embodiment of the present invention, the OSD may periodically scan the PG to collect the process pressure of the cluster within the period. The length of the cycle time can be set according to actual needs, for example, the cycle time can be set to 1 minute.

It should be noted that, in order to ensure that the process pressure can accurately reflect the current pressure situation of the cluster, in this embodiment of the present invention, the process pressure of the cluster involved refers to the process pressure of the cluster within the latest cycle time, and the cycle time is Take 1 minute as an example, you can use the current time as the reference time to obtain the process pressure of the cluster in the past 1 minute.

S102: Trigger the scrub state machine according to the process pressure of the cluster and the execution conditions of the scrub task.

When the PG is in the active+clean state, that is, the PG is in the task execution state, and the current time meets the execution time of the scrub task, the OSD can trigger the scrub state machine to start the operation process for executing the scrub task. After the scrub state machine is triggered, the system automatically locks the scrub task.

In the embodiment of the present invention, in order to reduce the impact of the scrub task on the front-end business, when the PG is in the task execution state and the current time meets the execution time of the scrub task, it can be determined whether the process pressure of the cluster belongs to the preset high pressure range.

Wherein, the preset high pressure range can be set as the usage rate of the CPU is greater than 50% or the usage rate of the disk is greater than 50%.

When the process pressure of the cluster is not within the preset high pressure range, it means that the OSD in the cluster can quickly process the scrub task, and the scrub state machine can be triggered directly.

When the process pressure of the cluster falls within the preset high pressure range, it means that the resource occupancy rate of the cluster is relatively high. If the scrub state machine is triggered at this time, since the OSD cannot process the scrub task quickly, the lock operation of the scrub task will take up a long time. Therefore, when the process pressure of the cluster falls within the preset high pressure range, you can wait for the scrub task to reach the deadline before triggering the scrub state machine.

Each scrub task carries a deadline when it is registered, as long as the OSD executes the scrub task within that deadline.

S103: According to the process pressure of the cluster, adjust the number of objects in the scrub task to perform this scan task.

The process pressure of the cluster will directly affect the time it takes for the OSD to execute the scrub task. The OSD will add pg locks during the execution of the scrub task. The longer the OSD takes to execute the scrub task, the longer the pg lock is occupied, and accordingly, the greater the impact on the front-end services in the cluster. Therefore, in this embodiment of the present invention, the number of objects in the scrub task to perform this scan task can be adjusted according to the process pressure of the cluster.

When the process pressure of the cluster is high, the number of objects in this scan task can be appropriately reduced; when the process pressure of the cluster is low, the number of objects in this scan task can be appropriately increased.

In a specific implementation, the correspondence between different process pressure ranges and the number of objects can be recorded in the form of a correspondence list. When the scrub state machine is triggered, a pre-established correspondence list can be used to search for a process pressure that matches the cluster's process pressure. The number of objects, and the number of objects is used as the number of objects in the scrub task to perform this scan task.

For example, the process pressure of the cluster can be divided into three levels: high pressure, medium pressure and low pressure. For example, when the CPU usage rate or the disk usage rate is greater than 50%, it means that the process pressure of the cluster belongs to high pressure; when When the CPU usage or disk usage is less than 10%, the process pressure of the cluster is low pressure; when the CPU usage or disk usage is between 10% and 50%, the cluster process pressure is medium pressure. The number of objects in this scan task under high pressure can be set to 2; the number of objects in this scan task under medium pressure can be set to 5; the number of objects in this scan task under low pressure can be set to 10 .

S104: Execute the current scan task according to the number of objects. After each scan task is completed, adjust the number of objects in the scrub task to perform the scan task according to the process pressure of the cluster until all the scan tasks included in the scrub task are completed. End the operation.

The number of objects to be scanned in a scrub task is often large. Generally, multiple scan tasks need to be performed. Therefore, each time a scan task is completed, you can return to S103 to adjust the number of objects in the scrub task to perform this scan task according to the process pressure of the cluster. The number of objects, until the scrub task is completed, the operation ends.

It should be noted that, in the embodiment of the present invention, the process pressure of the cluster on which the adjustment of the number of objects is performed every time returning to S103 refers to the process pressure of the cluster within the latest cycle time.

It can be seen from the above technical solutions that the process pressure of the cluster is obtained; the scrub state machine is triggered according to the process pressure of the cluster and the execution conditions of the scrub task. After the scrub state machine is triggered, the system automatically locks the scrub task. In order to reduce the time occupied by this locking operation, you can adjust the number of objects in the scrub task to perform this scan task according to the process pressure of the cluster; perform this scan task according to the number of objects. The number of objects to be scanned in a scrub task is often large. Generally, multiple scan tasks need to be performed. Therefore, each time a scan task is completed, the number of objects to be scanned in the scrub task can be adjusted according to the process pressure of the cluster. , until all the scan tasks included in the scrub task are completed, the operation ends. In this technical solution, the number of objects to be scanned by the current scrub task can be automatically adjusted according to the process pressure of the cluster. Under the condition that the scrub task can be executed smoothly, the time that the scrub task occupies the pg lock can be effectively reduced, so that the Effectively reduce the impact of scrub tasks on front-end business.

In this embodiment of the present invention, after the current scanning task is performed according to the number of objects, the process may return to S103 to re-adjust the number of objects corresponding to the next scanning task. There may be an interval between executing two scan tasks. Therefore, in this embodiment of the present invention, in order to further reduce the impact of executing the scrub task on the front-end business, after completing the current scan task according to the number of objects, adjust the next scan task according to the number of objects. Before scanning the number of objects corresponding to the task, you can first determine whether the process pressure of the cluster falls within the preset high pressure range.

When the process pressure of the cluster is not within the preset high pressure range, you can directly adjust the steps of the number of objects to perform the scan task in the scrub task according to the process pressure of the cluster.

When the process pressure of the cluster falls within the preset high pressure range, you can wait for a preset time before executing the steps of adjusting the number of objects in the scrub task to perform the scan task according to the process pressure of the cluster.

The value of the preset time can be set according to actual needs, for example, the preset time can be set to 3 seconds.

After each scan task is executed, the process pressure of the cluster is evaluated. When the process pressure of the cluster is high, it can wait for a preset time before executing the next scan task, which can effectively relieve the process pressure of the cluster and further reduce the execution of scrub The impact of the task on the front-end business.

In this embodiment of the present invention, the OSDs in the cluster may include a primary OSD and a backup OSD. After the primary OSD completes the scan task, it will send the corresponding scan task to the standby OSD, and the standby OSD will feed back object data to the primary OSD after completing the scan task. To ensure data consistency between the primary OSD and the backup OSD, after receiving the object data fed back by the backup OSD, the primary OSD can determine whether the object data obtained by executing this scan task is consistent with the object data fed back by the backup device.

When the object data obtained by executing this scan task is inconsistent with the object data fed back by the standby device, the scrub task can be marked as an error state.

By comparing the object data of the primary OSD and the backup OSD, data inconsistencies can be found in time. Marking a scrub task as an error state can help administrators to intuitively understand which scrub task has the data inconsistency problem, so as to solve the data inconsistency problem in a targeted manner.

2 is a schematic structural diagram of a scrub pressure adjustment device provided by an embodiment of the present invention, including an acquisition unit 21, a trigger unit 22, an adjustment unit 23, and an execution unit 24;

an obtaining unit 21 for obtaining the process pressure of the cluster;

The triggering unit 22 is used to trigger the scrub state machine according to the process pressure of the cluster and the execution conditions of the scrub task;

The adjustment unit 23 is used to adjust the number of objects in the scrub task to perform this scan task according to the process pressure of the cluster;

The execution unit 24 is configured to execute the scan task according to the number of objects, and adjust the number of objects to perform the scan task in the scrub task according to the process pressure of the cluster every time the scan task is completed, until all the scan tasks included in the scrub task When all are completed, the operation ends.

Optionally, the triggering unit includes a judging subunit, an executing subunit and a waiting subunit;

The judgment subunit is used to judge whether the process pressure of the cluster belongs to the preset high pressure range when the PG is in the task execution state and the current time meets the execution time of the scrub task;

The execution subunit is used to trigger the scrub state machine when the process pressure of the cluster does not belong to the preset high pressure range;

The waiting sub-unit is used to trigger the scrub state machine when the process pressure of the cluster falls within the preset high pressure range and wait for the scrub task to reach the deadline.

Optionally, it also includes a pressure judging unit and a waiting unit;

The pressure judgment unit is used to judge whether the process pressure of the cluster belongs to the preset high pressure range;

The waiting unit is used for, when the process pressure of the cluster falls within the preset high pressure range, wait for a preset time before executing the step of adjusting the number of objects in the scrub task to perform the scan task according to the process pressure of the cluster.

Optionally, the adjustment unit is specifically used to find the number of objects matching the process pressure of the cluster from the pre-established correspondence list, and use the number of objects as the number of objects to perform this scan task in the scrub task; wherein , the corresponding relationship between different process pressure ranges and the number of objects is recorded in the corresponding relationship list.

Optionally, also include a data judging unit and a marking unit;

A data judging unit for judging whether the object data obtained by executing this scanning task is consistent with the object data fed back by the standby device;

The marking unit is used to mark the scrub task as an error state when the object data obtained by executing the current scan task is inconsistent with the object data fed back by the standby device.

For the description of the features in the embodiment corresponding to FIG. 2 , reference may be made to the relevant description of the embodiment corresponding to FIG. 1 , which will not be repeated here.

It can be seen from the above technical solutions that the process pressure of the cluster is obtained; the scrub state machine is triggered according to the process pressure of the cluster and the execution conditions of the scrub task. After the scrub state machine is triggered, the system automatically locks the scrub task. In order to reduce the time occupied by this locking operation, you can adjust the number of objects in the scrub task to perform this scan task according to the process pressure of the cluster; perform this scan task according to the number of objects. The number of objects to be scanned in a scrub task is often large. Generally, multiple scan tasks need to be performed. Therefore, each time a scan task is completed, the number of objects to be scanned in the scrub task can be adjusted according to the process pressure of the cluster. , until all the scan tasks included in the scrub task are completed, the operation ends. In this technical solution, the number of objects to be scanned by the current scrub task can be automatically adjusted according to the process pressure of the cluster. Under the condition that the scrub task can be executed smoothly, the time that the scrub task occupies the pg lock can be effectively reduced, so that the Effectively reduce the impact of scrub tasks on front-end business.

FIG. 3 is a schematic diagram of the hardware structure of a scrub pressure adjustment device 30 according to an embodiment of the present invention, including:

memory 31 for storing computer programs;

The processor 32 is configured to execute a computer program to implement the steps of the scrub pressure adjustment method described in any of the above embodiments.

Embodiments of the present invention further provide a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of the scrub pressure adjustment method described in any of the foregoing embodiments are implemented.

The method, the device, and the computer-readable storage medium for adjusting the scrub pressure provided by the embodiments of the present invention have been described in detail above. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. As for the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Professionals may further realize that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two, in order to clearly illustrate the possibilities of hardware and software. Interchangeability, the above description has generally described the components and steps of each example in terms of functionality. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Skilled artisans may implement the described functionality using different methods for each particular application, but such implementations should not be considered beyond the scope of the present invention.

The steps of a method or algorithm described in conjunction with the embodiments disclosed herein may be directly implemented in hardware, a software module executed by a processor, or a combination of the two. A software module can be placed in random access memory (RAM), internal memory, read only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other in the technical field. in any other known form of storage medium.

Claims (8)

1. A scrub pressure adjustment method, comprising:

acquiring the process pressure of a cluster;

triggering a scrub state machine according to the process pressure of the cluster and the execution condition of the scrub task;

according to the process pressure of the cluster, adjusting the number of objects for executing the scanning task in the scrub task;

executing the scanning task according to the number of the objects, and adjusting the number of the objects executing the scanning task in the scrub task according to the process pressure of the cluster when the scanning task is completed once, until all the scanning tasks contained in the scrub task are completed, ending the operation;

the triggering the scrub state machine according to the process pressure of the cluster and the execution condition of the scrub task comprises:

when the PG is in a task execution state and the current time meets the execution time of a scrub task, judging whether the process pressure of the cluster belongs to a preset high pressure range;

when the process pressure of the cluster does not belong to a preset high pressure range, triggering a scrub state machine;

and when the process pressure of the cluster belongs to a preset high pressure range, triggering a scrub state machine when the scrub task reaches the cut-off time.

2. The scrub pressure adjustment method according to claim 1, further comprising, after the performing the scan task according to the number of the objects:

judging whether the process pressure of the cluster belongs to a preset high pressure range or not;

and when the process pressure of the cluster belongs to a preset high pressure range, waiting for a preset time and then executing the step of adjusting the number of objects for executing the scanning task in the scrub task according to the process pressure of the cluster.

3. The scrub pressure adjusting method according to claim 1, wherein the adjusting the number of the objects in the scrub task for executing the current scanning task according to the process pressure of the cluster comprises:

searching the number of objects matched with the process pressure of the cluster from a pre-established corresponding relation list, and taking the number of the objects as the number of the objects for executing the scanning task in the scrub task; wherein, the corresponding relation list records the corresponding relation between different process pressure ranges and the number of objects.

4. The scrub pressure adjustment method according to claim 1, further comprising, after the performing the scan task according to the number of the objects:

judging whether the object data acquired by executing the scanning task is consistent with the object data fed back by the standby equipment or not;

and when the object data acquired by executing the scanning task is inconsistent with the object data fed back by the standby equipment, marking the scrub task in an error state.

5. The scrub pressure adjusting device is characterized by comprising an acquisition unit, a trigger unit, an adjusting unit and an execution unit;

the acquiring unit is used for acquiring the process pressure of the cluster;

the triggering unit is used for triggering a scrub state machine according to the process pressure of the cluster and the execution condition of the scrub task;

the adjusting unit is configured to adjust the number of objects in the scrub task, which execute the current scanning task, according to the process pressure of the cluster;

the execution unit is configured to execute the scanning task according to the number of the objects, and adjust the number of the objects in the scrub task for executing the scanning task according to the process pressure of the cluster every time the scanning task is completed, and end the operation until all the scanning tasks included in the scrub task are completed;

the trigger unit comprises a judging subunit, an executing subunit and a waiting subunit;

the judging subunit is configured to, when the PG is in a task execution state and the current time meets the execution time of the scrub task, judge whether the process pressure of the cluster belongs to a preset high pressure range;

the execution subunit is used for triggering a scrub state machine when the process pressure of the cluster does not belong to a preset high pressure range;

and the waiting subunit is used for triggering the scrub state machine when the process pressure of the cluster belongs to a preset high pressure range and the scrub task is waited to reach the deadline time.

6. The scrub pressure adjustment device according to claim 5, further comprising a pressure judging unit and a waiting unit;

the pressure judging unit is used for judging whether the process pressure of the cluster belongs to a preset high pressure range or not;

and the waiting unit is used for waiting for a preset time and then executing the step of adjusting the number of objects for executing the scanning task in the scrub task according to the process pressure of the cluster when the process pressure of the cluster belongs to a preset high pressure range.

7. A scrub pressure adjustment device comprising:

a memory for storing a computer program;

a processor for executing the computer program to implement the steps of the scrub pressure adjustment method as claimed in any one of claims 1 to 4.

8. A computer-readable storage medium, having stored thereon a computer program which, when being executed by a processor, carries out the steps of the scrub pressure adjustment method as claimed in any one of claims 1 to 4.

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