Modify REC Buffer

Overview

This function sets parameters of the REC Buffer for copying data via the REC in Consistency mode.

REC Buffer Specifications for Each Model

Model	Total size of all of the REC Buffers (per CM)	The maximum number of REC Buffers	The maximum size of a single REC Buffer
ETERNUS DX100 S5	128 MB	1	128 MB
ETERNUS DX200 S5	512 MB	4	512 MB
ETERNUS DX500 S5/DX600 S5/DX900 S5 ETERNUS DX8100 S4/DX8900 S4	8192 MB	8	2048 MB
ETERNUS AF150 S3	128 MB	1	128 MB
ETERNUS AF250 S3	512 MB	4	512 MB
ETERNUS AF650 S3	8192 MB	8	2048 MB

Caution

Registering the license for the Advanced Copy function is required to set the REC Buffer.
This function can only be used when the local storage system (the storage system that creates REC Buffers) supports REC.
Perform REC Buffer settings in both the REC copy source and destination storage systems.
When changing REC Buffers, suspend the sessions using the target REC Buffers.
When deleting REC Buffers, stop the sessions using the target REC Buffers.
This function cannot be used when the remote storage system and/or copy path have not been configured.

Cache memory is not only used for REC Buffers, but also used for copy tables, the Thin Provisioning function (*1), the Storage Cluster function (*1), the Non-disruptive Storage Migration function, and the Extreme Cache function. Note that an REC Buffer with the maximum capacity for each model cannot always be created depending on the following conditions.

Memory capacity in the storage system
Copy table size
Maximum pool capacity
Total TFOV capacity (*2)
License registration for the Non-disruptive Storage Migration function
Extreme Cache setting (enabled) and Extreme Cache capacity

*1	:	The shared area in the cache memory is used for the following conditions. The maximum pool capacity is expanded to "1.5 PB" or larger The total TFOV capacity (*2) has been expanded from the default capacity Refer to the descriptions about "Storage Cluster" in the [System] screen for the default capacity of the TFOV for each model.
*2	:	The total TFOV capacity indicates the total capacity of the volumes that are used for the Storage Cluster function in a storage system.

Because REC Buffers are duplicated between the CMs, the actual memory capacity is twice as large as the selected REC Buffer capacity.

Note

Take REC reverse operation into consideration and specify the same values for the REC Buffers ("Forwarding Interval", "Monitoring Time", "HALT Wait Timer", "I/O Priority Mode", "Immediate HALT Mode", and "High Bandwidth Mode") in the copy source storage system and the copy destination storage system.
When performing bidirectional data transfer, settings for "Send" and "Receive" REC Buffers in the storage system are required.
If the usage of the REC Buffer to which the REC Disk Buffer has already been assigned is changed to "Unused", the REC Disk Buffer assignment will be cleared (the REC Disk Buffer itself will not be deleted).

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

Specify "Usage", "Remote Box ID", "Size", "Forwarding Interval", "Monitoring Time", and "HALT Wait Timer" for each management group of the REC Buffer obtained from the storage system.

REC Buffer Setting List

Item

Description

Setting values

Group

The management group number of the REC Buffer is displayed.

ETERNUS DX100 S5: 0

ETERNUS DX200 S5: 0 - 3

ETERNUS DX500 S5/DX600 S5/DX900 S5: 0 - 7

ETERNUS DX8100 S4/DX8900 S4: 0 - 7

ETERNUS AF150 S3: 0

ETERNUS AF250 S3: 0 - 3

ETERNUS AF650 S3: 0 - 7

Usage

Specify the usage of the REC Buffer.

When setting the REC Buffer for sending, select "Send". When setting the REC Buffer for receiving, select "Receive". To delete the REC Buffer, select "Unused".

Unused

Send

Receive

Remote Box ID

Select the Box ID for the remote storage system.

If the copy path information is deleted after the REC Buffer creation, "???" is displayed. Note that REC Buffers with "???" cannot be used. Delete any REC Buffers with this status.

If "Unused" is selected for the usage, "-" (hyphen) is displayed.

Remote storage system Box ID

"-" (hyphen)

Size

Select the REC Buffer size.

If "Unused" is selected for the usage, "-" (hyphen) is displayed.

The REC Buffer size can be set up to the maximum size that is calculated from the installed memory capacity and the usable cache memory capacity in the storage system (excluding the currently used capacity such as assigned size to the copy tables).

Caution

In the ETERNUS DX100 S5, a total size of 512 MB of memory is reserved for the copy table and REC Buffer. If an REC Buffer is created, 256 MB (REC Buffer size, 128 MB x 2) of the total memory size is used. Therefore, the maximum table size is 256 MB. Note that an REC Buffer cannot be created if the copy table size is larger than 264 MB.

ETERNUS DX100 S5:

128 MB (Default)

ETERNUS DX200 S5:

128 MB (Default)

256 MB

512 MB

ETERNUS DX500 S5/DX600 S5/DX900 S5:

128 MB (Default)

256 MB

512 MB

1024 MB

2048 MB

ETERNUS DX8100 S4/DX8900 S4:

128 MB (Default)

256 MB

512 MB

1024 MB

2048 MB

ETERNUS AF150 S3:

128 MB (Default)

ETERNUS AF250 S3:

128 MB (Default)

256 MB

512 MB

ETERNUS AF650 S3:

128 MB (Default)

256 MB

512 MB

1024 MB

2048 MB

"-" (hyphen)

Forwarding Interval

Select the data transfer intervals.

If "Unused" is selected for the usage, "-" (hyphen) is displayed.

1 sec. (Default)

2 sec.

4 sec.

8 sec.

15 sec.

30 sec.

45 sec.

60 sec.

75 sec.

90 sec.

105 sec.

120 sec.

"-" (hyphen)

Monitoring Time

Specify the monitoring time, before transition to the "Halt" state for a copy session when an REC Buffer shortage occurs.

If the REC Buffer is in a high-load state for the specified monitoring time, the copy session is automatically changed to "Halt" state. When "0 min." is specified in this field, REC Buffer shortage monitoring is not performed.

If "Unused" is selected for the usage, "-" (hyphen) is displayed.

0 min.

1 min.

2 min.

3 min.

4 min.

5 min. (Default)

6 min.

7 min.

8 min.

9 min.

10 min.

11 min.

12 min.

13 min.

14 min.

15 min.

"-" (hyphen)

HALT Wait Timer

Specify the maximum non-response time. During a non-response time, the host I/O response is stopped to give priority to data transfers from the REC Buffer in a high-load state (or when the used capacity of the REC Buffer is 100%).

If the non-response time exceeds the specified value, response to host I/O is restarted. However, the data transfer is stopped. The copy session is changed to the "Halt" state. If a response delay to the host I/O is not allowed, such as when the host is VMware, specify "0 sec." for this parameter.

If "Unused" is selected for the usage, "-" (hyphen) is displayed.

0 sec.

5 sec.

10 sec.

15 sec. (Default)

"-" (hyphen)

Advanced Setting

"I/O Priority Mode", "Immediate HALT Mode", and "High Bandwidth Mode" can only be set when setting a copy operation or host I/O tuning for each REC Buffer.

Item	Description	Setting values
Group	The management group number of the REC Buffer is displayed.	ETERNUS DX100 S5: 0 ETERNUS DX200 S5: 0 - 3 ETERNUS DX500 S5/DX600 S5/DX900 S5: 0 - 7 ETERNUS DX8100 S4/DX8900 S4: 0 - 7 ETERNUS AF150 S3: 0 ETERNUS AF250 S3: 0 - 3 ETERNUS AF650 S3: 0 - 7
I/O Priority Mode	Select either "Enable" or "Disable" for the "I/O Priority Mode" of the REC Buffer. It is not necessary to change the default value ("Enable") for normal use. If "Unused" is selected for the usage, "-" (hyphen) is displayed. "I/O Priority Mode" reduces the effect on host I/O when an initial copy for starting, restarting, or recovering the copy function is performed. Caution This mode should only be used by users who want to maintain host I/O performance as much as possible during REC. If "Enable" is selected and host I/O with a high load continues, it may take an extended period of time for the data to reach an equivalent state. Reduce throughput by as much as possible to avoid exceeding the line bandwidth of REC during initial copying.	Enable Disable "-" (hyphen)
Immediate HALT Mode	Select either "Enable" or "Disable" for the "Immediate HALT Mode" of the REC Buffer. It is not necessary to change the default value ("Enable") for normal use. If "Unused" is selected for the usage, "-" (hyphen) is displayed. "Immediate HALT Mode" reduces the effect on host I/O because of the insufficient of REC Buffer when "HALT Wait Timer" is set to "0 sec.". Enable this item when the response to host I/O is reduced even if "0 sec." is selected for the "HALT Wait Timer". Caution This mode should only be used by users who want to maintain host I/O performance as much as possible during REC. Items that are set for this mode are only applied when "0 sec." is selected for "HALT Wait Timer". When "Enable" is selected, the storage system changes the sessions using the target REC Buffers to "Halt" if the capacity of an REC Buffer is insufficient. If this occurs, the initial copy starts every time when recovering from the "Halt" state and the time required for the order of data transfers cannot be guaranteed, resulting in this process taking an extended period of time.	Enable Disable "-" (hyphen)
High Bandwidth Mode	Select either "Enable" or "Disable" for the "High Bandwidth Mode" of the REC Buffer. It is not necessary to change the default value ("Enable") for normal use. If "Unused" is selected for the usage, "-" (hyphen) is displayed. "High Bandwidth Mode" reduces the number of communications by transferring control data required for buffer transfers with as little time as possible to improve the transfer speed for long distance communication.	Enable Disable "-" (hyphen)

Operating Procedures

Adding or Changing an REC Buffer

Select the target REC Buffer that is to be added or changed (multiple selections can be made), and click the [Modify REC Buffer] in [Action].
Change the REC Buffer configurations, and click the [Set] button.
→ A confirmation screen appears.
Caution
- An error screen appears in the following conditions:
  - The total size of REC Buffers is larger than the maximum capacity for each model
  - The same remote Box ID has been selected both for "Send" and for "Receive" as its usage
  - The usage of an REC Buffer is "Send" or "Receive", and its path to the remote Box ID has been deleted
  - An REC Buffer, which has already been deleted ("???" is displayed in the "Remote Box ID" field), still exists
  - The usage of an REC Buffer to which an REC Disk Buffer has already been assigned is changed to "Receive"
  - The setting contents of the REC Buffer has not been changed
Note
- To change the remote Box ID, first delete the corresponding group. Then, click [Modify REC Buffer] again to specify a new remote Box ID and other information in the corresponding group.
- To change "I/O Priority Mode", "Immediate HALT Mode", or "High Bandwidth Mode", click "Advanced Setting".
Click the [OK] button.

→ The REC Buffer modification starts.
Click the [Done] button to return to the [REC Buffer] screen.

Deleting an REC Buffer

Select the target REC Buffers to be deleted (multiple selections can be made), and click the [Modify REC Buffer] in [Action].
Select "Unused" for the usage of the REC Buffer and then click the [Set] button.

→ A confirmation screen appears.
Click the [OK] button.

→ Deletion of an REC Buffer starts.
Click the [Done] button to return to the [REC Buffer] screen.