Standard for moving data within the volume by Automated Storage Tiering is defined as "Tiering policy".
The approach in relation to the configuration of Tiering policy is described below.
The "peak value" or "average value" within the evaluation period of IOPS in relation to the target volume, taking into account the access status in order to move data within the volume.
In order to place data with a high IOPS value, even for a short period of time in the evaluation period, onto a rapid disk, "peak value" should be selected. In order to place data with a constantly high IOPS value, "average value" should be selected.
Make a selection according to the state of access to the data of the target volume.
This is the period during which the state of access to the data within the target volume is evaluated.
Depending on the system configuration and form of utilization, the following may be selected.
Hour Units (2, 4, 6, 8, or 12 hours)
Day Units (1 - 31 days)
Week Unit (1 week)
When a value for day units has been selected, during one day (24 hours), the time of the day to perform the evaluation can be specified. In addition, the time to start evaluation and repositioning of access status data (Automated Storage Tiering Execution Time) can be specified as well.
When a value for week unit is selected, accessed data is evaluated during a period from Sunday through Saturday. The day of the week for evaluation can be specified in Days of the Week subject to Evaluation. In addition to day units, Evaluation Day can be specified.
Upon taking into account the effect on tasks utilizing the target volume, configure an appropriate evaluation period, time frame subject to evaluation, and time to start the relocation.
Example
If a system that business hours are 9:00 - 17:00 and the backup is 0:00 - 2:00, and if the target for Automated Storage Tiering is only the business I/O, a daily relocation is set to perform as follows.
Item Name | Specification |
|---|---|
Evaluation Period | 1day |
Time of the Day subject to Evaluation | 9:00 - 17:00 |
Automated Storage Tiering Execution Time | 2:00 |
Point
Automated Storage Tiering relocates data according to the settings in the Tiering policy. Because a data migration relocates data between disks in a storage device, the time required to finish a relocation varies depending on the amount of data to be relocated. If the amount of data to be relocated is large, relocation of all the data may not finish before the next evaluation. If the next evaluation process starts before the relocation finishes, the current relocation process terminates with the relocation result displayed as "Normal Suspended".
If Automated Storage Tiering is kept running with an unfinished data relocation, the full effects of Automated Storage Tiering may not be achieved. It is recommended that you reset Evaluation Period of the Tiering policy so that the relocation can finish.
The following is an estimate for the amount of data that can be relocated during the evaluation period.
Evaluation Period | Estimated Relocatable Data Amount (*1) |
|---|---|
2 hours | 1.2 TB |
*1: Varies depending on the disk configuration of the storage device, the load status of the storage device, and the number of relocation target volumes.
The evaluation period during which a relocation finishes can be calculated based on an estimation for the relocatable data amount.
For example, if the relocatable amount of data is 5 TB, based on the result of the calculation below, setting the evaluation period to 8.5 hours or more allows the relocation to finish.
5 TB / (1.2 TB / 2 hours) = 8.5 hours
When setting Automated Storage Tiering Time Limit of the Tiering policy, replace the evaluation period with the period from the start of a relocation to the termination of the relocation.
Note
When Time of the Day subject to Evaluation is set in the ETERNUS DX S2 series (excluding DX60 S2), if the finish time of the relocation process exceeds the finish time of Time of the Day subject to Evaluation, the evaluation result of the next relocation process may be displayed as "Error Suspended". For this reason, set Automated Storage Tiering Time Limit of the Tiering policy so that the relocation process does not run beyond the finish time of Time of the Day subject to Evaluation.
For example, if Time of the Day subject to Evaluation is set to 9:00 to 17:00, set Automated Storage Tiering Time Limit to 17:00 or earlier.
The optimal value for Evaluation Standard and Evaluation Period depends on the system configuration and form of utilization.
For this reason, Automated Storage Tiering has prepared three types of execution modes (Auto, Semi-Auto, and Manual). The "Semi-Auto" and "Manual" execution modes may be used to test the Tiering policy without actually moving data in the target volume. Use these modes to decide the value for IOPS when controlling tiering in detail.
The following explains each of the execution modes.
Execution Mode | Details of Execution | Purpose of Selection | |
|---|---|---|---|
Subject of Automated Execution | Tasks That Require Manual Operation | ||
Auto |
| - | Selected for standard operation. |
Semi-Auto |
|
| Selected in the following cases:
|
Manual |
|
| Selected in the following cases:
|
Of the access status data for moving the data within the volume, Day of the Week subject to Evaluation and Configure Evaluation Excluded Day can be specified. Make a specification when configuring subjects of evaluation in detail according to tasks.
For the Day of the Week subject to Evaluation, specify a day of the week that is to be a subject of the evaluation of the access status data.
For the Configure Evaluation Excluded Day, specify days that are to not be included in the subject of evaluation of the access status data.
Note
When the summer time function of the OS is effective, do not configure the time at which the switching of summer time takes place as the Automated Storage Tiering Execution Time. Doing so prevents evaluation of the access status data and relocation of data within the volume from being performed properly.
