Modify RAID Group Parameters

Overview

This function tunes the following parameters of each RAID group.

Parameters Setting
- Rebuild Priority
  
  Specify the level to give priority to rebuild, copyback, and redundant copy instead of host access. Specifying a larger "Rebuild Priority" value may improve rebuild, copyback, and redundant copy performance.
Advanced Settings
- DCMF
  
  DCMF is a coefficient for the command issuance amount of the drive. Specify this parameter to improve the sequential writing access performance. The bigger the value is, the more commands issue.
- Drive Access Priority
  
  This mode controls the command issuance order during drive access. Changing the command issuance order improves the throughput for all of the drives.
- Throttle
  
  Throttle is the proportion of the number of commands that are issued to a drive at the same time to the maximum number of commands that can be issued. By limiting the number of commands that are issued at the same time to the drive, the load on the specific RAID group (drive) is reduced.
- Ordered Cut
  
  Ordered Cut is the number of commands for optimizing drive access processing (priority control). By performing the priority control of commands in increments of the specified number, a long queue time for low-priority commands can be eliminated.

Caution

For normal use, it is not necessary to change the default values of the RAID group parameters.
When the "Rebuild Priority" setting is changed, the priority is changed not only for a rebuild, copyback, and redundant copy that will be performed after the setting is changed, but also for any rebuild, copyback, and redundant copy operations that are currently being performed.
When the target RAID group is registered as an REC Disk Buffer, do not select "High" for the "Rebuild Priority" setting. Even if "High" is selected, rebuilding, copyback, and redundant copy are performed with "Middle" priority during host access.
Specify the same RAID group parameters for all of the RAID groups that configure a WSV. If different RAID group parameters are specified, the host access performance may be reduced.
If "Usage" for the selected RAID group is "Extreme Cache Pool", "Rebuild Priority" cannot be specified.
This function cannot be used under the following conditions:
- LDE is being performed in the storage system
- The target RAID group belongs to an FTSP

Note

When specifying "Throttle" or "Ordered Cut", select "Enable" for "Drive Tuning Parameter Setting" in advance.
RAID groups that configure a WSV can be checked in the [Volume Detail] screen ([Used RAID Group] tab). Refer to the [Volume (Basic Information)] function for details.

User Privileges

Availability of Executions in the Default Role

Default role	Availability of executions
Monitor
Admin
StorageAdmin
AccountAdmin
SecurityAdmin
Maintainer

Refer to "User Roles and Policies" for details on the policies and roles.

Settings

In this screen, specify the RAID group parameters.

Parameters Setting

Item

Description

Setting values

Rebuild Priority

Specify the rebuild priority.

It is not necessary to change the default value for normal use. When not changing the setting, select "Do not change".

When host access is not performed, rebuild, copyback, and redundant copy to RAID groups that is not registered as REC Disk Buffers are performed with "High" priority regardless of the "Rebuild Priority" setting.

The rebuild priority of a RAID group cannot be changed if it is registered as an Extreme Cache Pool.

Low

Perform rebuild, copyback, and redundant copy with a normal priority.
Middle

Give the same priority as the host access to rebuild, copyback, and redundant copy.
High

Give priority to rebuild, copyback, and redundant copy over host access.

(Advantage of selecting "Middle" or "High")

Rebuild, copyback, and redundant copy performance may improve when "Middle" or "High" is specified because priority is given to rebuild, copyback, and redundant copy instead of host access.

(Disadvantage of selecting "Middle" or "High")

Note that specifying higher "Rebuild Priority" may cause the degradation of RAID group performance (throughput) when rebuild, copyback, or redundant copy is being performed in the target RAID group.

Do not change

Low (*1)

Middle

High (*2)

*1	:	Default (RAID level is not "RAID6-FR")
*2	:	Default (RAID level is "RAID6-FR")

Advanced Settings

Item	Description	Setting values
DCMF	Select "Change" and specify the Disk Command Multiplying Factor (DCMF). It is not necessary to change the default value for normal use. The maximum number of commands issued to a drive is changed to a multiple represented by the specified value. (If "DCMF" is "2", the number of commands is doubled. If "DCMF" is "3", the number of commands is tripled.) When not changing the setting, select "Do not change". (Advantage of a large value) The higher the DCMF value is, the more drive throughput is available, improving sequential performance. (Disadvantage of a large value) Note that high DCMF value may result in a high load on the drive, decreasing performance.	Do not change Change 1 (Default) - 10
Drive Access Priority	Select the drive access priority from "Response" or "Throughput". It is not necessary to change the default value for normal use. When not changing the setting, select "Do not change". This item is not displayed when a RAID group that is configured with SSDs or SSD SEDs is selected. For SSDs and SSD SEDs, this item is fixed to "Response". Response Commands are issued in order during drive access to speed up a response to the host. Throughput The command issuance order is changed and data is collectively written to the same drive during drive access to improve the throughput for all of the drives. (Advantage of selecting "Throughput") The throughput for all of the drives is improved when "Throughput" is selected because data is collectively written to the same drive. (Disadvantage of selecting "Throughput") The performance of each command response may be reduced when "Throughput" is selected because queuing processes for host I/O are not performed by using the FIFO (first in, first out) method.	Do not change Response (Default) Throughput
Drive Tuning Parameter Setting	Specify whether to "Enable" or "Disable" the following drive tuning parameters. Throttle Ordered Cut It is not necessary to change the default value for normal use. When not changing the "Throttle" and "Ordered Cut" setting values, select "Do not change". Note that "Do not change" is always selected when this function is started. Caution When selecting multiple RAID groups as the target of this function and "Enable" is specified for the "Drive Tuning Parameter Setting", the "Throttle" and "Ordered Cut" values set in this screen are applied to the target RAID groups.	Do not change Enable (Default) Disable
Throttle	Select "Enable" for "Drive Tuning Parameter Setting" and specify "Throttle". "Throttle" is the proportion of the number of commands that are to be issued to a drive at the same time to the maximum number of command issuance. It is not necessary to change the default value for normal use. If a single RAID group is selected to start this function, the value that is currently set in the storage system is displayed. If multiple RAID groups are selected to start this function and the same value is specified for all the RAID groups in the storage system, that value is displayed. If a RAID group with a different "Throttle" exists in the storage system, "100 %" is displayed. (Advantage of a smaller value) Specifying a smaller number can limit the number of commands to be issued to a drive at the same time, resulting in reduction of the load onto the specific RAID group (drive). This setting can be used when the response performance of the specific RAID group (drive) is decreased due to a conflict between host I/Os or batch processes. (Disadvantage of a smaller value) Specifying a smaller throttle value decreases the number of commands processed by the drive at the same time, which might cause a longer queue time. Caution If "Enable" is selected for "Drive Tuning Parameter Setting", not only is the "Throttle" value changed but the "Ordered Cut" value is changed as well. To keep the "Ordered Cut" value unchanged, specify the current parameter displayed in the "Current Settings" field.	100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 %
Ordered Cut	Select "Enable" for "Drive Tuning Parameter Setting" and specify "Ordered Cut". "Ordered Cut" is the number of commands to optimize drive access processing (priority control). When "Ordered Cut" is "x", the order is changed for every x commands based on the priority settings of the commands. It is not necessary to change the default value for normal use. If a single RAID group is selected to start this function, the value that is currently set in the storage system is displayed. If multiple RAID groups are selected to start this function and the same value is specified for all the RAID groups in the storage system, that value is displayed. If a RAID group with a different "Throttle" exists in the storage system, "0" is displayed. When "Ordered Cut" is "0", the number of commands for controlling the priority cannot be specified. All of the commands issued to the drive are processed according to their priority settings. The "Ordered Cut" value cannot be used for SSDs and SSD SEDs. (Advantage of a smaller value) Specifying a smaller value for [Ordered Cut] reduces the number of commands for priority control. Commands with lower priority are processed without delay. (Disadvantage of a smaller value) Specifying a smaller value for [Ordered Cut], priority control of commands is performed in increments for the specified number, which might cause a delay in processing commands with a higher priority. Caution If "Enable" is selected for "Drive Tuning Parameter Setting", not only is the "Ordered Cut" value changed but the "Throttle" value is changed as well. To keep the "Throttle" value unchanged, specify the current parameter displayed in the "Current Settings" field.	0 - 65535 400 (Default)

Item

Description

Setting values

DCMF

Select "Change" and specify the Disk Command Multiplying Factor (DCMF).

It is not necessary to change the default value for normal use. The maximum number of commands issued to a drive is changed to a multiple represented by the specified value. (If "DCMF" is "2", the number of commands is doubled. If "DCMF" is "3", the number of commands is tripled.) When not changing the setting, select "Do not change".

(Advantage of a large value)

The higher the DCMF value is, the more drive throughput is available, improving sequential performance.

(Disadvantage of a large value)

Note that high DCMF value may result in a high load on the drive, decreasing performance.

Do not change

Change

1 (Default) - 10

Drive Access Priority

Select the drive access priority from "Response" or "Throughput".

It is not necessary to change the default value for normal use. When not changing the setting, select "Do not change". This item is not displayed when a RAID group that is configured with SSDs or SSD SEDs is selected. For SSDs and SSD SEDs, this item is fixed to "Response".

Response

Commands are issued in order during drive access to speed up a response to the host.
Throughput

The command issuance order is changed and data is collectively written to the same drive during drive access to improve the throughput for all of the drives.

(Advantage of selecting "Throughput")

The throughput for all of the drives is improved when "Throughput" is selected because data is collectively written to the same drive.

(Disadvantage of selecting "Throughput")

The performance of each command response may be reduced when "Throughput" is selected because queuing processes for host I/O are not performed by using the FIFO (first in, first out) method.

Do not change

Response (Default)

Throughput

Drive Tuning Parameter Setting

Specify whether to "Enable" or "Disable" the following drive tuning parameters.

Throttle
Ordered Cut

It is not necessary to change the default value for normal use. When not changing the "Throttle" and "Ordered Cut" setting values, select "Do not change". Note that "Do not change" is always selected when this function is started.

Caution

When selecting multiple RAID groups as the target of this function and "Enable" is specified for the "Drive Tuning Parameter Setting", the "Throttle" and "Ordered Cut" values set in this screen are applied to the target RAID groups.

Do not change

Enable (Default)

Disable

Throttle

Select "Enable" for "Drive Tuning Parameter Setting" and specify "Throttle".

"Throttle" is the proportion of the number of commands that are to be issued to a drive at the same time to the maximum number of command issuance. It is not necessary to change the default value for normal use. If a single RAID group is selected to start this function, the value that is currently set in the storage system is displayed. If multiple RAID groups are selected to start this function and the same value is specified for all the RAID groups in the storage system, that value is displayed. If a RAID group with a different "Throttle" exists in the storage system, "100 %" is displayed.

(Advantage of a smaller value)

Specifying a smaller number can limit the number of commands to be issued to a drive at the same time, resulting in reduction of the load onto the specific RAID group (drive). This setting can be used when the response performance of the specific RAID group (drive) is decreased due to a conflict between host I/Os or batch processes.

(Disadvantage of a smaller value)

Specifying a smaller throttle value decreases the number of commands processed by the drive at the same time, which might cause a longer queue time.

Caution

If "Enable" is selected for "Drive Tuning Parameter Setting", not only is the "Throttle" value changed but the "Ordered Cut" value is changed as well. To keep the "Ordered Cut" value unchanged, specify the current parameter displayed in the "Current Settings" field.

100 %

90 %

80 %

70 %

60 %

50 %

40 %

30 %

20 %

10 %

Ordered Cut

Select "Enable" for "Drive Tuning Parameter Setting" and specify "Ordered Cut".

"Ordered Cut" is the number of commands to optimize drive access processing (priority control). When "Ordered Cut" is "x", the order is changed for every x commands based on the priority settings of the commands. It is not necessary to change the default value for normal use. If a single RAID group is selected to start this function, the value that is currently set in the storage system is displayed. If multiple RAID groups are selected to start this function and the same value is specified for all the RAID groups in the storage system, that value is displayed. If a RAID group with a different "Throttle" exists in the storage system, "0" is displayed.

When "Ordered Cut" is "0", the number of commands for controlling the priority cannot be specified. All of the commands issued to the drive are processed according to their priority settings. The "Ordered Cut" value cannot be used for SSDs and SSD SEDs.

(Advantage of a smaller value)

Specifying a smaller value for [Ordered Cut] reduces the number of commands for priority control. Commands with lower priority are processed without delay.

(Disadvantage of a smaller value)

Specifying a smaller value for [Ordered Cut], priority control of commands is performed in increments for the specified number, which might cause a delay in processing commands with a higher priority.

Caution

If "Enable" is selected for "Drive Tuning Parameter Setting", not only is the "Ordered Cut" value changed but the "Throttle" value is changed as well. To keep the "Throttle" value unchanged, specify the current parameter displayed in the "Current Settings" field.

0 - 65535

400 (Default)

Display Contents

The parameters of the selected RAID group is displayed.

Target RAID Groups

Item		Description
Name		The RAID group name is displayed.
Status		The RAID group status is displayed. Refer to "RAID Group Status" for details.
RAID Level		The RAID level is displayed. High Performance (RAID1+0) High Capacity (RAID5) High Reliability (RAID6) High Reliability (RAID6-FR) Reliability (RAID5+0) Mirroring (RAID1) Striping (RAID0)
Total Capacity		The total capacity of the RAID groups is displayed.
Current Settings	Rebuild Priority	The current rebuild priority of the RAID group is displayed. A "-" (hyphen) is displayed if the RAID group is registered as an Extreme Cache Pool.
	DCMF	The current DCMF (1 to 10) of the RAID group is displayed.
	Drive Access Priority	The current drive access priority of the RAID group is displayed. When the drives that configure the target RAID group are SSDs or SSD SEDs, a "-" (hyphen) is displayed.
	Throttle	The current throttle of the RAID group is displayed. When "Drive Tuning Parameter Setting" is disabled, a "-" (hyphen) is displayed.
	Ordered Cut	The current ordered cut (0 to 65535) of the RAID group is displayed. When "Drive Tuning Parameter Setting" is disabled, or the configuration drives of the RAID group are SSDs or SSD SEDs, a "-" (hyphen) is displayed.

Operating Procedures

Select which RAID groups to change the RAID group parameters for (multiple selections can be made) and click [Modify RAID Group Parameters] in [Action].
Specify the RAID group parameters and click the [Modify] button.
→ A confirmation screen appears.
Caution
- The response performance to the server may be affected by changing RAID group parameters.
Click the [OK] button.

→ The RAID group parameter modification starts.
Click the [Done] button to return to the [RAID Group] screen.