Modify Cache Parameters (TPP)
Overview
This function changes the cache parameters of each Thin Provisioning Pool (TPP).
Performance of the storage system varies depending on the cache hit ratio. The storage system detects sequentiality when a host requests Read/Write. If sequentiality is detected when a Read request is issued, the cache hit rate is improved by reading the sequential data into the cache memory in advance. The characteristics of Read/Write requests from the host depends on the system. Performance of the storage system may improve by specifying a cache parameter that is suitable for the system that is being used.
The parameters to specify are as follows:
Multi Writeback Count (MWC)
Specify the number of processes that can be written back at the same time.
If pinned data exists in the storage system, MWC cannot be configured.
The same cache parameter can be applied for multiple TPPs in a single operation.
Cache parameters, except the MWC, are specified for each TPV. Refer to the [Modify Cache Parameters] 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, change the cache parameters.
Parameters Setting
| Item | Description | Setting values |
|---|---|---|
Multi Writeback Count (MWC) |
Specify the value of the Multi Writeback Count. (Advantage of specifying a large value) When specifying larger MWC, sequential write access performance is improved. Note that this is not effective when a number of random write accesses occur. (Disadvantage of specifying a large value) Depending on the ratio of read access and write access, read access performance may be reduced. |
1 - 16 (*1) Refer to "Allowed Input for MWC (TPP)" for the default value. |
| *1 | : | The setting values that are available for Multi Writeback Count vary depending on the RAID level and drive configuration. |
Allowed Input for MWC (TPP)
Allowed Input for MWC When Using the Default Stripe Depth Value (TPP)
| RAID level | Drive configuration (*1) | Allowed input for MWC (initial state) |
|---|---|---|
| Stripe Depth = 64KB (default) | ||
RAID0 |
4D |
1 - 8 (2) |
RAID1 |
1D+1M |
1 - 16 (8) |
RAID1+0 |
2D+2M |
1 - 16 (4) |
4D+4M |
1 - 8 (2) |
|
8D+8M |
1 - 4 (1) |
|
12D+12M |
1 - 2 (1) |
|
RAID5 |
3D+1P |
1 - 8 (3) |
4D+1P |
1 - 8 (2) |
|
6D+1P |
1 - 5 (2) |
|
7D+1P |
1 - 4 (2) |
|
8D+1P |
1 - 4 (1) |
|
12D+1P |
1 - 2 (1) |
|
RAID6 |
4D+2P |
1 - 8 (2) |
6D+2P |
1 - 5 (2) |
|
7D+2P |
1 - 4 (2) |
|
8D+2P |
1 - 4 (1) |
|
RAID6-FR |
(4D+2P)x2+1HS (4D+2P)x5+1HS |
1 - 8 (2) |
(6D+2P)x2+1HS |
1 - 5 (2) |
|
(8D+2P)x3+1HS |
1 - 4 (1) |
| *1 | : | D: Data drives, M: Mirror drives, P: Parity drives |
Allowed Input for MWC When the Stripe Depth Value is Tuned (TPP)
| RAID level | Drive configuration (*1) | Allowed input for MWC (initial state) | |||
|---|---|---|---|---|---|
| When the Stripe Depth is ... | |||||
| 128KB | 256KB | 512KB | 1024KB | ||
RAID0 |
4D |
1 - 4 (2) |
1 - 2 (2) |
1 (fixed) |
1 (fixed) |
RAID1+0 |
2D+2M |
1 - 8 (4) |
1 - 4 (4) |
1 - 2 (2) |
1 (fixed) |
4D+4M |
1 - 4 (2) |
1 - 2 (2) |
1 (fixed) |
1 (fixed) |
|
8D+8M |
1 - 2 (1) |
1 (fixed) |
1 (fixed) |
1 (fixed) |
|
12D+12M |
1 (fixed) |
1 (fixed) |
1 (fixed) |
1 (fixed) |
|
RAID5 |
3D+1P |
1 - 4 (3) |
1 - 2 (2) |
1 (fixed) |
- |
4D+1P |
1 - 4 (2) |
1 - 2 (2) |
1 (fixed) |
- |
|
6D+1P |
1 - 2 (2) |
1 (fixed) |
- |
- |
|
7D+1P |
1 - 2 (2) |
1 (fixed) |
- |
- |
|
8D+1P |
1 - 2 (1) |
1 (fixed) |
- |
- |
|
12D+1P |
1 (fixed) |
- |
- |
- |
|
| *1 | : | D: Data drives, M: Mirror drives, P: Parity drives, -: Stripe Depth expansion is not available |
Display Contents
In this screen, detailed information and cache parameter setting information for the selected TPP are displayed.
| Item | Description |
|---|---|
No. |
The TPP number is displayed. |
Name |
The TPP name is displayed. |
Current MWC |
The value of the current Multi Writeback Count setting is displayed. |
Operating Procedures
Select which TPP to change the cache parameters for (multiple selections can be made) and click [Modify Cache Parameters] in [Action].
Change the cache parameters and click the [Modify] button.
→ A confirmation screen appears.
NoteIf the [Default] button is clicked before the [Modify] button, the default cache parameters are restored.
Click the [OK] button.
→ The cache parameter modification starts.
Click the [Done] button to return to the [Threshold] screen.