Understanding Open Replicator Operations

 

 

OverView

Terminology

Requirements

Operations

Considerations

Restrictions

Symrcopy options

Examples

Lab

 

 

Open Replicator OverView:

 

Symmetrix Open Replicator provides a tool that can be used to migrate data from older Symmetrix arrays, Clariion arrays, and certain third-party storage arrays to a Symmetrix DMX or V-Max storage array.

 

Symmetrix Open Replicator can also be used to migrate data from a Symmetrix DMX or V-Max storage array to other types of storage arrays within the SAN infrastructure.

 

Open Replicator can also be used to Backup and archive existing data within the SAN infrastructure as part of an information lifecycle management solution.

 

Copying data from a Symmetrix DMX or V-Max storage array to devices on remote storage arrays allows for data to be copied fully or incrementally.

 

Data copying is accomplished as part of the storage system process and does not require host resources.

 

The data can be copied online between the Symmetrix array and remote devices, allowing host applications, such as a database or file server, to remain operational during the copy process.

 

 

Open Replicator Terminology:

 

Contorl Array: The Symmetrix DMX or V-Max array and its devices will always be referred to as the control side of the copy operation.

 

Remote Array: Older Symmetrix arrays, Clariion arrays, or third-party arrays on the SAN will always be referred to as the remote array.

 

Control Devices: Devices which are in control side of the copy operations or in control array.

 

Remote Devices: Devices which are in remote side of the copy operation or in remote array.

The focus is always on the control side; all operations will be performed from control side.

 

Device File: A file which contains the Control device and Remote devices.

In a device file, control devices are always listed on left side.

Format: symdev=SymID:SymDev

In a device file remote devices are always listed on right side.

Format: symdev|clardev=arrayid:device or WWN=LUN wwn

 

 

Open Replicator Operations:

 

There are two types of copy operations push and pull. Copy operations are either hot or cold.

 

Hot Push Operation: Data will be copied Online from the Control devices to Remote devices, allowing host applications, such as a database or file server, to remain operational during the copy process.

 

All directors that are mapped to the control devices must be able to copy to the remote devices.

Control device may be read/write state.

Remote device is not accessible to the host. Can use -consistent, -differential and -precopy.

 

During hot push operations, if the Symmetrix attempts to write to control device tracks that have not yet been copied, Open Replicator will immediately copy those tracks to the remote device first and then service the I/O request.

 

If there is a network failure while copying data, the copy session will fail. Although, the local host can still continue writing to the control device without impact to the application.

 

Failed push sessions can be activated again only if no new data has been written to the control device since the session failed.

 

Hot Pull Operation: Data will be copied Online to the Control devices from Remote devices, allowing host applications, such as a database or file server, to remain operational during the copy process.

 

Control device is online to the host; All directors must see the remote device.

 

Data can be protected in case of session failures by using -donor_update option.

 

The donor_update option must have been included when the session was originally created in order to fully recover all writes made to the devices prior to the failure.

 

Cold Push Operations: Data will be copied Offline from the Control devices to Remote devices. The control device must be set as user Not Ready to the Symmetrix host.

 

Any directors that are mapped to the control device and can reach the remote device will be used. Can use –differential option.

 

Cold Pull Operations; Data will be copied Offline to the Control devices from Remote devices. At least one director must see the remote device

 

If there is a network failure while performing a cold pull operation, the session will stall and retry.

 

Open Replicator Considerations:

 

·        Remote devices do not have to be the same RAID type or meta-configuration.

 

·        For a push operation, remote capacity must be equal to or larger than the control device extents and vice versa for a pull operation. Exception: when you have pushed data to a remote device that is larger than the control device, and you want to pull the data back, you can use the -force_copy option.

 

·        On push copy operations, remote devices should not be accessed by their remote hosts until copying has completed.

 

·        On pull operations, the remote devices should not be updated by array hosts for the duration of the copy process.

 

·        For pull operations from devices with SCSI reservations, if the remote devices have a cluster running against them or the devices are AIX LVM devices, you  must shut down the cluster, AIX host or other software that is creating the SCSI  reservations before creating the Open Replicator Session.

 

·        Data corruption to devices may be possible during a copy operation if another host on the SAN has write access to the remote device. So it is recommended that to keep the devices are in NR state or unmount from host.

 

·        Accumulated I/O errors between the control device and remote device will cause a session to fail if the copy operation is a hot push. The failed session may be activated again as long as no new data has been written to the control device since the session failed. The session will temporarily stall and restart on any other type of copy operation.

 

·        Open Replicator fully supports copy operations for Symmetrix thin devices.

 

·        Open Replicator supports copy operations for a cold push from a Virtual Device (VDEV).

 

Restrictions:

 

·        Only one copy session per control device can be active at a time.

 

·        Maximum 15 incremental Open Replicator copy sessions can exist for a single device.

 

·        Maximum 1024 copy sessions are allowed per array when running Enginuity 5773 or later.

 

·        Maximum 512 copy sessions are allowed per array when running Enginuity 5772 or earlier.

 

·        On a push operation data can be cold copied concurrently from one control device to up to 16 remote devices

 

·        Copy session is between two arrays and cannot be created with control and remote devices on the same Symmetrix array.

 

·        Devices that are accessible only through the SAN cannot be specified with Symmetrix device names.

 

·        On an offline push operation to multiple devices that were created as part of one session, devices in the session must be updated together, a single device cannot be updated independently.

 

·        Open Replicator can be used only with FBA devices via Fibre Channel Integrated Directors.CKD,VCM,WORM and metamebers are not supported.

 

·        Only one remote device is allowed for a hot push operation.

 

·        The Open Replicator cannot detect changes to a remote device during, or between incremental copies.

 

 

License Requirement:

Open Replicator functionality requires

Open Replicator/LM — for Online Pull only

Open Replicator/DM — for all functions except Online Pull.

 

SAN Requirements:

A Fibre Channel switch is required for Open Replicator. Direct connections (such as arbitrated loop) are not supported.

 

The SAN for the remote storage array must have connectivity to the control Symmetrix SAN. Open Replicator requires that at least one port on the remote array that allows access to the remote device have access to the control device through at least one port for a cold copy and all ports for a hot copy on the control array.

 

Zoning must be set up on the Fibre Channel switch to zone the control Symmetrix fibre adapters (FAs) to the remote storage array front-end adapter(s).

 

If the storage port for the source devices is running volume configuration management (VCM) software (such as Volume Logix for Symmetrix or EMC Access LogixTM for CLARiiON) or a similar software product, setup may require granting permission to access the target device(s) from the target storage port. For instance, on Symmetrix, you need to enable the control FA(s) to have access to the remote storage array device(s).

 

The SYMCLI command symsan lists port and LUN WWNs as seen from a specific Symmetrix director and port. This can be used to validate that the zoning between the port and target is correct. It does not require a created Open Replicator session. Use this command to display remote ports’ WWNs, and the LUN’s WWN seen behind a remote port WWN.

 

 

Symrcopy Command Options:

 

Create

Defines a new Open Replicator copy session.

Activate

Starts the copying process on an existing Open Replicator copy session

List

Lists all Open Replicator copy sessions for a given Symmetrix array

Query

Queries for the status of Open Replicator copy sessions

Verify

Verifies that a copy session is in an existing state

Terminate

Terminates a copy session and removes it from the Symmetrix array.

If the session is activated and in the CopyInProg, CopyOnAccess, or

CopyOnWrite state, you must include the -symforce option to terminate the session.

Recreate

Creates an incremental copy session on an existing copy session. Only valid for copy sessions created using the -differential option.Recreating a session creates a new point-in-time copy of the data

Restore

Restores data from a remote device that was previously copied during a differential push operation back to the control device

Consistent

If a control device is pushing data to a remote device and that control device is currently online for host write I/O operations, a consistent point-in-time copy can bemade across multiple control devices using the Enginuity Consistency Assist (ECA) feature (-consistent). This will temporarily prevent any host write I/Os while the Open Replicator copy session begins.

Copy

Data will be copied in background after session activation

Precopy

Data will be copyied in background after session creation.

The Precopy feature is available only for hot push operations. Hot push sessions can also be set to   Precopy mode by including the -precopy option with either the create or recreate command. The -precopy option requires Enginuity version 5772 or later.

Differential

Allows to recreate the session at a later time by using the recreate command

Ceiling

To set the maximum allowed bandwidth percentage for a given director, port, director/port pair, or all directors and ports.    

Acceptable values are 0 - 100, or NONE to shut the ceiling function off.Setting the ceiling to a value (other than NONE) renders the pace value ineffective to the copy. If the ceiling value is set to NONE, the session pace is in effect for the copy.

Pace

The session pace designates how fast data copies between devices. Values can range from 0 to 9, with 0 being the fastest pace, and 9 being the slowest pace. If set to 0, there will be no inserted delay time and the replication will proceed as fast as possible.

The default for both online (hot) replication and offline (cold)replication is 5.

Donar Update

This feature causes all writes to the control device from the host to be immediately copied to the remote device as well. Because the data is fully copied to both the remote device and the control device, if a failure occurs, the session can safely be terminated and created again to fully recover from any mid-copy failure. This feature can be used in hot pull operation. Requires Enginuity version 5773 or later.The donor update option may also be used on an incremental restore session.