Copy Services functions can help you implement storage solutions to keep your business running 24 hours a day, 7 days a week. Copy Services include a set of disaster recovery, data migration, and data duplication functions.
The storage system supports Copy Service functions that contribute to the protection of your data. These functions are also supported on the IBM® TotalStorage™ Enterprise Storage Server®.
- If you are creating paths between an older release of the DS8000® (Release 5.1 or earlier), which supports only 4-port host adapters, and a newer release of the DS8000 (Release 6.0 or later), which supports 8-port host adapters, the paths connect only to the lower four ports on the newer storage system.
- If you are creating paths from a model 993 4-port host adapter to a previous release DS8000 (Release 6.0 or later), which supports 8-port host adapters, you can only connect the lower four ports of the 8-port host adapter.
- The maximum number of FlashCopy® relationships that are allowed on a volume is 65534. If that number is exceeded, the FlashCopy operation fails.
- The size limit for volumes or extents in a Copy Service relationship is 2 TB.
- Thin provisioning functions in open-system environments are supported
for the following Copy Services functions:
- FlashCopy relationships
- Global Mirror relationships if the Global Copy A and B volumes are Extent Space Efficient (ESE) volumes. The FlashCopy target volume (Volume C) in the Global Mirror relationship can be an ESE volume or standard volume.
- PPRC supports any intermix of T10-protected or standard volumes. FlashCopy does not support intermix.
- PPRC supports copying from standard volumes to ESE volumes, or ESE volumes to Standard volumes, to allow migration with PPRC failover when both source and target volumes are on a DS8000 version 8.2 or higher.
- Point-in-time copy, which includes IBM
The FlashCopy function allows you to make point-in-time, full volume copies of data so that the copies are immediately available for read or write access. In IBM Z environments, you can also use the FlashCopy function to perform data set level copies of your data.
- Remote mirror and copy, which includes the following functions:
- Metro Mirror
Metro Mirror provides real-time mirroring of logical volumes between two storage system that can be located up to 300 km from each other. It is a synchronous copy solution where write operations are completed on both copies (local and remote site) before they are considered to be done.
- Global Copy
Global Copy is a nonsynchronous long-distance copy function where incremental updates are sent from the local to the remote site on a periodic basis.
- Global Mirror
Global Mirror is a long-distance remote copy function across two sites by using asynchronous technology. Global Mirror processing is designed to provide support for unlimited distance between the local and remote sites, with the distance typically limited only by the capabilities of the network and the channel extension technology.
- Metro/Global Mirror (a combination of Metro Mirror and Global
Metro/Global Mirror is a three-site remote copy solution. It uses synchronous replication to mirror data between a local site and an intermediate site, and asynchronous replication to mirror data from an intermediate site to a remote site.
- Multiple Target PPRC
Multiple Target PPRC builds and extends the capabilities of Metro Mirror and Global Mirror. It allows data to be mirrored from a single primary site to two secondary sites simultaneously. You can define any of the sites as the primary site and then run Metro Mirror replication from the primary site to either of the other sites individually or both sites simultaneously.
- Metro Mirror
- Remote mirror and copy for IBM Z environments, which includes z/OS® Global Mirror.
The point-in-time and remote mirror and copy features are supported across variousIBM server environments such as IBM i, System p, and IBM Z , as well as servers from Oracle and Hewlett-Packard.
You can manage these functions through a command-line interface that is called the DS CLI. You can use the DS8000 Storage Management GUI to set up and manage the following types of data-copy functions from any point where network access is available:
Point-in-time copy (FlashCopy)
You can use the FlashCopy function to make point-in-time, full volume copies of data, with the copies immediately available for read or write access. In IBM Z environments, you can also use the FlashCopy function to perform data set level copies of your data. You can use the copy with standard backup tools that are available in your environment to create backup copies on tape.
FlashCopy is an optional function.
- From the time that you initiate a FlashCopy operation until the storage system copies all data from the source volume to the target volume.
- Until you explicitly delete the FlashCopy relationship if it was created as a persistent FlashCopy relationship.
- The amount of data to be copied
- The number of background copy processes that are occurring
- The other activities that are occurring on the storage systems
- Consistency groups
- Creates a consistent point-in-time copy of multiple volumes, with negligible host impact. You can enable FlashCopy consistency groups from the DS CLI.
- Change recording
- Activates the change recording function on the volume pair that is participating in a FlashCopy relationship. This function enables a subsequent refresh to the target volume.
- Establish FlashCopy on existing Metro Mirror source
- Establish a FlashCopy relationship, where the target volume is also the source of an existing remote mirror and copy source volume. This allows you to create full or incremental point-in-time copies at a local site and then use remote mirroring commands to copy the data to the remote site.
- Fast reverse
- Reverses the FlashCopy relationship without waiting for the finish of the background copy of the previous FlashCopy. This option applies to the Global Mirror mode.
- Inhibit writes to target
- Ensures that write operations are inhibited on the target volume until a refresh FlashCopy operation is complete.
- Multiple Incremental FlashCopy
- Allows a source volume to establish incremental flash copies to a maximum of 12 targets.
- Multiple Relationship FlashCopy
- Allows a source volume to have multiple (up to 12) target volumes at the same time.
- Persistent FlashCopy
- Allows the FlashCopy relationship to remain even after the FlashCopy operation completes. You must explicitly delete the relationship.
- Refresh target volume
- Refresh a FlashCopy relationship, without recopying all tracks from the source volume to the target volume.
- Resynchronizing FlashCopy volume pairs
- Update an initial point-in-time copy of a source volume without having to recopy your entire volume.
- Reverse restore
- Reverses the FlashCopy relationship and copies data from the target volume to the source volume.
- Reset SCSI reservation on target volume
- If there is a SCSI reservation on the target volume, the reservation is released when the FlashCopy relationship is established. If this option is not specified and a SCSI reservation exists on the target volume, the FlashCopy operation fails.
- Remote Pair FlashCopy
Figure 1 illustrates how Remote Pair FlashCopy works. If Remote Pair FlashCopy is used to copy data from Local A to Local B, an equivalent operation is also performed from Remote A to Remote B. FlashCopy can be performed as described for a Full Volume FlashCopy, Incremental FlashCopy, and Dataset Level FlashCopy.
The Remote Pair FlashCopy function prevents the Metro Mirror relationship from changing states and the resulting momentary period where Remote A is out of synchronization with Remote B. This feature provides a solution for data replication, data migration, remote copy, and disaster recovery tasks.
Without Remote Pair FlashCopy, when you established a FlashCopy relationship from Local A to Local B, by using a Metro Mirror primary volume as the target of that FlashCopy relationship, the corresponding Metro Mirror volume pair went from
full duplexstate to
duplex pendingstate if the FlashCopy data was being transferred to the Local B. The time that it took to complete the copy of the FlashCopy data until all Metro Mirror volumes were synchronous again, depended on the amount of data transferred. During this time, the Local B would be inconsistent if a disaster were to have occurred.Note: Previously, if you created a FlashCopy relationship with the Preserve Mirror, Required option, by using a Metro Mirror primary volume as the target of that FlashCopy relationship, and if the status of the Metro Mirror volume pair was not in a
full duplexstate, the FlashCopy relationship failed. That restriction is now removed. The Remote Pair FlashCopy relationship completes successfully with the
Preserve Mirror, Requiredoption, even if the status of the Metro Mirror volume pair is either in a suspended or duplex pending state.
The Safeguarded Copy feature creates safeguarded backups that are not accessible by the host system and protects these backups from corruption that can occur in the production environment. You can define a Safeguarded Copy schedule to create multiple backups on a regular basis, such as hourly or daily. You can also restore a backup to the source volume or to a different volume. A backup contains the same metadata as the safeguarded source volume.
Safeguarded Copy can create backups with more frequency and capacity in comparison to FlashCopy volumes. The creation of safeguarded backups also impacts performance less than the multiple target volumes that are created by FlashCopy.
With backups that are outside of the production environment, you can use the backups to restore your environment back to a specified point in time. You can also extract and restore specific data from the backup or use the backup to diagnose production issues.
You cannot delete a safeguarded source volume before the safeguarded backups are deleted. The maximum size of a backup is 16 TB.
Copy Services Manager (available on the Hardware Management Console) is required to facilitate the use and management of Safeguarded Copy functions.
Remote mirror and copy
The remote mirror and copy feature is a flexible data mirroring technology that allows replication between a source volume and a target volume on one or two disk storage systems. You can also issue remote mirror and copy operations to a group of source volumes on one logical subsystem (LSS) and a group of target volumes on another LSS. (An LSS is a logical grouping of up to 256 logical volumes for which the volumes must have the same disk format, either count key data or fixed block.)
Remote mirror and copy is an optional feature that provides data backup and disaster recovery.
The remote mirror and copy feature provides synchronous (Metro Mirror) and asynchronous (Global Copy) data mirroring. The main difference is that the Global Copy feature can operate at long distances, even continental distances, with minimal impact on applications. Distance is limited only by the network and channel extenders technology capabilities. The maximum supported distance for Metro Mirror is 300 km.
With Metro Mirror, application write performance depends on the available bandwidth. Global Copy enables better use of available bandwidth capacity to allow you to include more of your data to be protected.
The enhancement to Global Copy is Global Mirror, which uses Global Copy and the benefits of FlashCopy to form consistency groups. (A consistency group is a set of volumes that contain consistent and current data to provide a true data backup at a remote site.) Global Mirror uses a master storage system (along with optional subordinate storage systems) to internally, without external automation software, manage data consistency across volumes by using consistency groups.
Consistency groups can also be created by using the freeze and run functions of Metro Mirror. The freeze and run functions, when used with external automation software, provide data consistency for multiple Metro Mirror volume pairs.
The following sections describe the remote mirror and copy functions.
- Synchronous mirroring (Metro Mirror)
- Provides real-time mirroring of logical volumes (a source and
a target) between two storage systems that can be located up to 300
km from each other. With Metro Mirror copying,
the source and target volumes can be on the same storage system or
on separate storage systems. You can locate the storage system at
another site, some distance away.
Metro Mirror is a synchronous copy feature where write operations are completed on both copies (local and remote site) before they are considered to be complete. Synchronous mirroring means that a storage server constantly updates a secondary copy of a volume to match changes that are made to a source volume.
The advantage of synchronous mirroring is that there is minimal host impact for performing the copy. The disadvantage is that since the copy operation is synchronous, there can be an impact to application performance because the application I/O operation is not acknowledged as complete until the write to the target volume is also complete. The longer the distance between primary and secondary storage systems, the greater this impact to application I/O, and therefore, application performance.
- Asynchronous mirroring (Global Copy)
- Copies data nonsynchronously and over longer distances than is
possible with the Metro Mirror feature.
When operating in Global Copy mode,
the source volume sends a periodic, incremental copy of updated tracks
to the target volume instead of a constant stream of updates. This
function causes less impact to application writes for source volumes
and less demand for bandwidth resources. It allows for a more flexible
use of the available bandwidth.
The updates are tracked and periodically copied to the target volumes. As a consequence, there is no guarantee that data is transferred in the same sequence that was applied to the source volume.
To get a consistent copy of your data at your remote site, periodically switch from Global Copy to Metro Mirror mode, then either stop the application I/O or freeze data to the source volumes by using a manual process with freeze and run commands. The freeze and run functions can be used with external automation software such as Geographically Dispersed Parallel Sysplex (GDPS®), which is available for IBM Z environments, to ensure data consistency to multiple Metro Mirror volume pairs in a specified logical subsystem.
Common options for Metro Mirror/Global Mirror and Global Copy include the following modes:
- Suspend and resume
- If you schedule a planned outage to perform maintenance at your remote site, you can suspend Metro Mirror/Global Mirror or Global Copy processing on specific volume pairs during the duration of the outage. During this time, data is no longer copied to the target volumes. Because the primary storage system tracks all changed data on the source volume, you can resume operations later to synchronize the data between the volumes.
- Copy out-of-synchronous data
- You can specify that only data updated on the source volume while the volume pair was suspended is copied to its associated target volume.
- Copy an entire volume or not copy the volume
- You can copy an entire source volume to its associated target volume to guarantee that the source and target volume contain the same data. When you establish volume pairs and choose not to copy a volume, a relationship is established between the volumes but no data is sent from the source volume to the target volume. In this case, it is assumed that the volumes contain the same data and are consistent, so copying the entire volume is not necessary or required. Only new updates are copied from the source to target volumes.
- Global Mirror
- Provides a long-distance remote copy across two sites by using asynchronous technology. Global Mirror processing is
most often associated with disaster recovery or disaster recovery testing. However, it can also be
used for everyday processing and data migration.
Global Mirror integrates both the Global Copy and FlashCopy functions.
The Global Mirror function mirrors data between volume pairs of two storage systems over greater distances without affecting overall performance. It also provides application-consistent data at a recovery (or remote) site in a disaster at the local site. By creating a set of remote volumes every few seconds, the data at the remote site is maintained to be a point-in-time consistent copy of the data at the local site.
Global Mirror operations periodically start point-in-time FlashCopy operations at the recovery site, at regular intervals, without disrupting the I/O to the source volume, thus giving a continuous, near up-to-date data backup. By grouping many volumes into a session that is managed by the master storage system, you can copy multiple volumes to the recovery site simultaneously maintaining point-in-time consistency across those volumes. (A session contains a group of source volumes that are mirrored asynchronously to provide a consistent copy of data at the remote site. Sessions are associated with Global Mirror relationships and are defined with an identifier [session ID] that is unique across the enterprise. The ID identifies the group of volumes in a session that are related and that can participate in the Global Mirror consistency group.)
Global Mirror supports up to 32 Global Mirror sessions per storage facility image. Previously, only one session was supported per storage facility image.
You can use multiple Global Mirror sessions to fail over only data assigned to one host or application instead of forcing you to fail over all data if one host or application fails. This process provides increased flexibility to control the scope of a failover operation and to assign different options and attributes to each session.
The DS CLI and DS Storage Manager display information about the sessions, including the copy state of the sessions.
- Practice copying and consistency groups
- To get a consistent copy of your data, you can pause Global Mirror on a consistency group boundary. Use the pause command with the secondary storage option. (For more information, see the DS CLI Commands reference.) After verifying that Global Mirror is paused on a consistency boundary (state is Paused with Consistency), the secondary storage system and the FlashCopy target storage system or device are consistent. You can then issue either a FlashCopy or Global Copy command to make a practice copy on another storage system or device. You can immediately resume Global Mirror, without the need to wait for the practice copy operation to finish. Global Mirror then starts forming consistency groups again. The entire pause and resume operation generally takes just a few seconds.
- Metro/Global Mirror
- Provides a three-site, long-distance disaster recovery replication that combines Metro Mirror with Global Mirror replication for
both IBM Z
open systems data. Metro/Global Mirror uses synchronous
replication to mirror data between a local site and an intermediate site, and asynchronous
replication to mirror data from an intermediate site to a remote site.
In a three-site Metro/Global Mirror, if an outage occurs, a backup site is maintained regardless of which one of the sites is lost. Suppose that an outage occurs at the local site, Global Mirror continues to mirror updates between the intermediate and remote sites, maintaining the recovery capability at the remote site. If an outage occurs at the intermediate site, data at the local storage system is not affected. If an outage occurs at the remote site, data at the local and intermediate sites is not affected. Applications continue to run normally in either case.
With the incremental resynchronization function enabled on a Metro/Global Mirror configuration, if the intermediate site is lost, the local and remote sites can be connected, and only a subset of changed data is copied between the volumes at the two sites. This process reduces the amount of data needing to be copied from the local site to the remote site and the time it takes to do the copy.
- Multiple Target PPRC
- Provides an enhancement to disaster recovery solutions by allowing data to be mirrored from a single primary site to two secondary sites simultaneously. The function builds on and extends Metro Mirror and Global Mirror capabilities. Various interfaces and operating systems support the function. Disaster recovery scenarios depend on support from controlling software such as Geographically Dispersed Parallel Sysplex (GDPS) and IBM Copy Services Manager.
- z/OS Global Mirror
- If workload peaks, which might temporarily overload the bandwidth
of the Global Mirror configuration, the enhanced z/OS Global Mirror function initiates a Global
Mirror suspension that preserves primary site application performance.
If you are installing new high-performance z/OS Global Mirror primary storage subsystems,
this function provides improved capacity and application performance
during heavy write activity. This enhancement can also allow Global
Mirror to be configured to tolerate longer periods of communication
loss with the primary storage subsystems. This enables the Global
Mirror to stay active despite transient channel path recovery events.
In addition, this enhancement can provide fail-safe protection against
application system impact that is related to unexpected data mover
The z/OS Global Mirror function is an optional function.
- z/OS Metro/Global Mirror Incremental Resync
- z/OS Metro/Global Mirror Incremental Resync is an enhancement for z/OS Metro/Global Mirror. z/OS Metro/Global Mirror Incremental Resync can eliminate the need for a full copy after a HyperSwap® situation in 3-site z/OS Metro/Global Mirror configurations. The storage system supports z/OS Metro/Global Mirror that is a 3-site mirroring solution that uses IBM System Storage Metro Mirror and z/OS Global Mirror (XRC). The z/OS Metro/Global Mirror Incremental Resync capability is intended to enhance this solution by enabling resynchronization of data between sites by using only the changed data from the Metro Mirror target to the z/OS Global Mirror target after a HyperSwap operation.
- If an unplanned failover occurs, you can use the z/OS Soft Fence function to prevent any system from accessing data from an old primary PPRC site. For more information, see the GDPS/PPRC Installation and Customization Guide, or the GDPS/PPRC HyperSwap Manager Installation and Customization Guide.
- z/OS Global Mirror Multiple Reader (enhanced readers)
- z/OS Global Mirror Multiple Reader provides multiple Storage Device Manager readers that allow improved throughput for remote mirroring configurations in IBM Z environments. z/OS Global Mirror Multiple Reader helps maintain constant data consistency between mirrored sites and promotes efficient recovery. This function is supported on the storage system running in a IBM Z environment with version 1.7 or later at no additional charge.
Interoperability with existing and previous generations of the DS8000 series
All of the remote mirroring solutions that are documented in the sections above use Fibre Channel as the communications link between the primary and secondary storage systems. The Fibre Channel ports that are used for remote mirror and copy can be configured as either a dedicated remote mirror link or as a shared port between remote mirroring and Fibre Channel Protocol (FCP) data traffic.
- Metro Mirror indicator feature numbers 75xx and 0744 and corresponding DS8000 series function authorization (2396-LFA MM feature numbers 75xx)
- Global Mirror indicator feature numbers 75xx and 0746 and corresponding DS8000 series function authorization (2396-LFA GM feature numbers 75xx).
Global Copy is a non-synchronous long-distance copy option for data migration and backup.