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.
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
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.
(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)
|
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".
(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.
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
|
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
|
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
|
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.
CautionThe 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.