System option modes for Thin Image

To provide greater flexibility, the storage systems have additional operational parameters called system option modes (SOMs) that allow you to tailor the storage system to your unique operating requirements. The SOMs are set on the service processor (SVP) by your service representative. Review the SOMs for your storage system, and work with your service representative to ensure that the appropriate SOMs for your operational environment are configured on your storage system.

The following table lists and describes the SOMs that apply to Thin Image.

NoteThe SOM information might have changed since this document was published. Contact Hitachi Solution Support Center for the latest SOM information.

Table 1: System option modes for Thin Image

Mode

Category

Description

Default

MCU/RCU

471

Thin Image

Since the SIM-RCs generated when the Thin Image pool usage rate exceeds the threshold value can be resolved by users, these SIM-RCs are not reported to the maintenance personnel. This mode is used to report these SIM-RCs to maintenance personnel.

The SIM-RCs reported by setting the mode to ON are: 601xxx (Pool utilization threshold exceeded), 603000 (SM space warning).

Mode 471 = ON: These SIM-RCs are reported to maintenance personnel.

Mode 471 = OFF: These SIM-RCs are not reported to maintenance personnel.

Note: Set this mode to ON when it is required to inform maintenance personnel of these SIM-RCs.

OFF

-

749

Dynamic Provisioning

Dynamic Tiering

Thin Image

This mode disables the HDP Rebalance function and the HDT Tier relocation function which allow the drives of all ECC Groups in the pool to share the load.

Mode 749 = ON: The HDP Rebalance function and the HDT Tier relocation function are disabled.

Mode 749 = OFF (default): The HDP Rebalance function and the HDT Tier relocation function are enabled.

Notes:

  1. This mode is applied when no change in performance characteristic is desired.
  2. When a pool is newly installed, the load may be concentrated on the installed pool volumes.
  3. When 0 data discarding is executed, load may be unbalanced among pool volumes.
  4. Pool VOL deletion while the mode is set to ON fails. To delete pool VOLs, set the mode to OFF.

OFF

-

896

Dynamic Provisioning

Dynamic Tiering

Thin Image

This mode enables or disables the background format function performed on an unformatted area of a DP/DT/TI pool.

For information regarding operating conditions, see the Provisioning Guide.

Mode 896 = ON: The background format function is disabled.

Mode 896 = OFF (default): The background format function is enabled.

Notes:

  1. This mode is applied when a customer requires the background format for a DP/DT/TI pool in the environment where new page allocation (in the case that system files are created from a host for newly created multiple DP-VOLs, for example) frequently occurs and the write performance degrades because of an increase in write pending rate.
  2. When the background format function is enabled, because up to 42 MB/s of ECCG performance is used, local copy performance may degrade by about 10%. Therefore, confirm whether the 10% performance degradation is acceptable or not before enabling the function.
  3. When a Dynamic Provisioning VOL on an external storage system, which is used as an external VOL, is used as a pool VOL, if the external pool on the external storage side becomes full due to the background format, the external VOL may be blocked.

    If the external pool capacity is smaller than the external VOL capacity (Dynamic Provisioning VOL of external storage system), do not enable the background format function.

  4. If the background format function is disabled by changing the mode setting, the format progress is initialized and the entire area becomes unformatted.
  5. The background format for FMC drives is not disabled. When FMC drives are used, use SOM 1093.

OFF

-

1093

Dynamic Provisioning

Dynamic Tiering

Thin Image

This mode is used to disable background unmap during microcode downgrade from a version that supports pool reduction rate correction to a version that does not support the function.

Mode 1093 = ON: Background unmap cannot work.

Mode 1093 = OFF (default): Background unmap can work.

Note: This mode is applied when downgrading microcode from a version that supports pool reduction rate correction to a version that does not support the function is disabled.

OFF

-

Parent Topic
  • Overview of Thin Image

    With Thin Image (HTI), you can perform cost-effective replication by storing the differential data between primary volumes (P-VOLs) and secondary volumes (S-VOLs) of virtual volumes (V-VOLs). You can also copy data of an entire volume, instead of copying just the differential data, to a volume. By copying the entire volume, you can expect a higher performance than by just storing the differential data.