ETERNUS DX Advanced Copy Functions · • "0" = nothing to copy Host view of . Backup Volume ....

ETERNUS DX Advanced Copy Functions

QuickOPC

Copyright Fujitsu, Release May 2011

Content

QuickOPC Copy Sessions in General QuickOPC Concept Diagram QuickOPC Concept QuickOPC Differential Copy Operation QuickOPC in Detail QuickOPC Restoration Operation QuickOPC Summary

Copyright Fujitsu, Release May 2011 QuickOPC ETERNUS DX Advanced Copy Functions 2

QOPC Copy Sessions in General (1) All Advanced Copy (AC) functions are executed in two

separate phases QuickOPC (QOPC) requires the use of two bitmaps One is the normal OPC control bitmap

• Used for the synchronization and observation of the physical copy process While the other is a tracking bitmap

• Records subsequent changes in the source and destination volume • Is active and recording between the separate QOPC command executions

These are created new for each QOPC session Logical Copy Initiates a QuickOPC session

• Causes a control bitmap and a tracking bitmap to be created • Bitmaps are created in the CM cache of the ETERNUS system


QOPC Copy Sessions in General (2) Physical Copy Starts serverless, automatically and directly after the logical copy phase

is finished The initial physical copy starts the sequential transfer of the contents of

the source area to the destination, changing the bits of the control bitmap as it proceeds

All updates on the copy source are handled by out-of-turn copying • Change of the appropriate bits of the control bitmap (for both copy source and

destination updates) • All of which is exactly the same as for a normal OPC

Parallel updates (both copy source and destination) • Change the appropriate bits of the tracking bitmap • Keep a record of what data will need to be copied over later • At this time the copy control bitmap (transfer bitmap) which shows the copy

status remains unchanged


QOPC Concept Diagram (1) First time invocation of QuickOPC (a full OPC)


Host view

Time ETERNUS view

Host view before 1st QOPC is started

Host view after 1st QOPC is started

Copy command invocation Completion response

Physical copy process

1st QOPC tracking

Bitmap created

QuickOPC ETERNUS DX Advanced Copy Functions 5

QOPC Concept Diagram (2) Second time invocation of QuickOPC (only differential copy)


Host view

Time ETERNUS view

Host view after 1st QOPC finished

Src Dest Src Dest

Host view between two QOPC invocation

logical copy completed

Src Dest

Host view during the 2nd QOPC invocation

2nd Copy command invocation Completion response; Bitmap created

Physical copy starts Src Dest

Physical copy completed Src Dest

1st QOPC tracking 2nd QOPC tracking

physical copy in progress

Physical copy (differences) 3 blocks only


QOPC Concept Immediately after QOPC starts Completion is notified Actual (physical) copy starts in the background

After completion of QOPC Copy Source Volume and Copy Destination Volume are used as two

independent Volumes for normal operation The Destination Volume

• Represents a full copy of the Source Volume (as it was at the time of issuing the QOPC command) and is immediately read and write accessible for normal business purposes

The Source Volume can remain fully accessible during the copy Ensure data consistency before the start of the QOPC session

• Make sure applications running on source volume are in backup mode • Or otherwise consistent • Or use the ACM pre- and post- script mechanism


QOPC Differential Copy Operation (1) When a QuickOPC request is sent to the ETERNUS And a QuickOPC session is already running on the replication pair

• A tracking bitmap is already in place • Then instead of the initial full copy, only the data areas indicated by the tracking

bitmap are copied over from the source

While less data needs to be copied, this copy is similar to the initial copy of QOPC from the copy processes point of view A logical copy step precedes the actual physical copy The emptied tracking bitmap starts recording subsequent updates from

this point in time onwards The copy destination and also the source becomes read/write accessible

as soon as the logical copy has completed


QOPC Differential Copy Operation (2) For QuickOPC, even after the physical copy has completed The session remains running

• Keeping track of what data is modified in the interim time • To be prepared for the next time the copy command is issued

If the power fails during the actual copy operation The current copy status is kept The operation continues automatically after the power is restored QOPC between encrypted volumes and unencrypted volumes

is not possible When copying encrypted volumes, transfer performance may not be as

good as when copying unencrypted volumes QOPC is highly effective for the following applications In the same situations as OPC usage For large data bases requiring reduced backup time

• Since only updated data is copied after the initial copy Or when data is frequently backed up and restored


QuickOPC in Detail (1) After the 1st QOPC session, a backup complete message is

generated and the host has the same contents view to the backup volume


0 0 0

0 0 0 0 0 0

Control BITMAP

Control Bitmap • Shows what has been

copied to Backup Volume • "0" = nothing to copy

Host view of Backup Volume

during QOPC session

TRANSACTION VOL BACKUP VOL

Physical Volumes

0 0 0

0 0 0 0 0 0

Tracking Bitmap

Tracking Bitmap • Shows what is modified during

the QOPC session on both Volumes

• "0" = not modified yet

LUN LUN


QuickOPC in Detail (2) Between the 1st QOPC session and the 2nd QOPC session

some modifications are possible e.g. on the source volume



during QOPC session

LUN LUN

Physical Volumes

0 0 0

0 0 0 0 0 0

Tracking Bitmap



• "1" = modified

1 0 0 0

0 0 0 0 0 0

Control BITMAP


copied to Backup Volume • "1" = not copied yet




modifications are also possible on the Backup Volume



during QOPC session

LUN LUN

Physical Volumes

0 0 0

0 0 0 0 0 0

Tracking Bitmap



• "1" = modified

1 1

0 0 0

0 0 0 0 0 0

Control BITMAP






modifications are possible independently on both Volumes


0 0 0

0 0 0 0 0 0

Control BITMAP



LUN LUN

Physical Volumes

0 0 0

0 0 0 0 0 0

Tracking Bitmap



• "1" = modified

1 1 1


during QOPC session



QuickOPC in Detail (5) Now a 2nd QOPC session is started and a logical copy phase

begins


Control Bitmap • Shows which changed blocks

have been copied to Backup Volume

• "1" = not copied yet

Tracking Bitmap • Is cleared for the next QOPC

session (3rd QOPC) • "0" = nothing modified yet

LUN LUN

Physical Volumes

0 0 0

0 0 0 0 0 0

Control Bitmap

Tracking Bitmap

1 1 1

0 0 0

0 0

0 0 0

1 1 1


during QOPC session


QuickOPC ETERNUS DX Advanced Copy Functions

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QuickOPC in Detail (6) After the logical copy phase is finished, the host has

immediately the same contents view on both volumes


0 0 0

0 0 0 0 0 0

Control Bitmap




LUN LUN

Physical Volumes

Tracking Bitmap



1 1 1

0 0 0

0 0 0 0 0 0


during QOPC session



QuickOPC in Detail (7) Now starting copying the three data blocks in the background

from the Transaction Volume to the Backup Volume within the 2nd QOPC session physical copy phase


0 0 0

0 0 0 0 0 0

Control Bitmap




LUN LUN

Physical Volumes

Tracking Bitmap



1 1 1

0 0 0

0 0 0 0 0 0


during QOPC session



QuickOPC in Detail (8) Another modification occurs on the Backup Volume when the

2nd QOPC session executes the physical copy phase


0 0 0

0 0 0 0 0 0

Control Bitmap




LUN LUN

Physical Volumes

Tracking Bitmap

Tracking Bitmap • Will be modified for the current

QOPC session (2nd QOPC) • "1" = modified

1

0 0 0

0 0 0 0 0 0

1


during QOPC session



QuickOPC in Detail (9) Physical data block copying continues from Transaction

Volume to the Backup Volume


0 0 0

0 0 0 0 0 0

Control Bitmap




LUN LUN

Physical Volumes

Tracking Bitmap

Tracking Bitmap • Is now modified for the current


1

1 0 0

0 0 0 0 0 0


during QOPC session



QuickOPC in Detail (10) After physical copy is finished, the 2nd QOPC session is still

active with the tracking phase


0 0 0

0 0 0 0 0 0

Control BITMAP




LUN LUN

Physical Volumes

Tracking Bitmap

Tracking Bitmap • Will be modified for the current


1 0 0

0 0 0 0 0 0

1 1


during QOPC session



QuickOPC Restoration Operation How QuickOPC data is restored depends on the current status

of the QuickOPC copy session During physical copy The data of the copied area is copied back from the copy destination

LUN to the copy source LUN Physical copy requires two copy sessions

• QuickOPC copy session • OPC restoration session

During QuickOPC tracking (after physical copy completion) Only the areas recorded in the tracking bitmap are copied back So only one physical copy session is required

• OPC restore session

To restore a QuickOPC volume start a normal OPC session in the reverse direction


QuickOPC Summary QuickOPC only copies data updated since the last physical

copy Amount of physical copy data can be reduced by using the

QuickOPC function As a result the load on the ETERNUS itself decreases This has an effect on operational I/O


QuickOPC - (1st time)

Online business

Online business Physical copy QOPC invocation

Online business

Online business QOPC invocation

QuickOPC - (2nd time) Shortening of copy time

Updated data only

Physical copy


ETERNUS DX Advanced Copy Functions · • "0" = nothing to copy Host view of . Backup Volume ....

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