frequently asked questions - emc vnxe nas replications

5/23/2018 Frequently Asked Questions - EMC VNXe NAS Replications

EMC Community Network December 2012

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Frequently Asked Questions: EMC VNXe NAS

Replication

Contents

Question: What does the Replication feature in VNXe provide?.................................................. 2

Question: Is VNXe replication Synchronous or Asynchronous?................................................... 2

Question: What is RPO setting in Replication for VNXe?.............................................................. 2

Question: Does VNXe support One to Many replication?.............................................................. 2

Question: What are the destination platforms supported by VNXe for replication?................... 2

Question: Can I use Deduplication feature when I replicate?....................................................... 3

Question: What happens when I turn off deduplication on the source?...................................... 3

Question: If I setup a replication session, do shares get replicated over to the destination?... 3

Question: What are the basic internal steps during a replication process?................................ 3

Question: As part of the replication, will point in time copies (snapshots) of a file system be

replicated to the destination? ................................................................................................................... 5

Question: In the case of VMware NFS Datastore Replication, can I use the datastore on the

replicated side (destination) to boot VMs for testing purposes?......................................................... 5

Question: Can I create a schedule to take snapshots on the destination application?............. 5

Question: Do I have to provision protection space on the source to enable/start replication? 5

Question: Why do I not see any Windows (CIFS) shares in the destination VNXe after

replication? ............................................................................................................................................... 6

Question: How do I find out what are the replication sessions that are on my VNXe?............. 6

Question: What are the steps involved in setting up a remote replication to a VNXe?............. 6

Question: Is there a limit for the total number of replication session on a VNXe?..................... 7

Question: Can I use a different Ethernet Port than the one used by a Shared Folder for

replication? ............................................................................................................................................... 7



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Question: What does the Replication feature in VNXe prov ide?

Answer: Replication in VNXe is a process in which storage data is duplicated either locallyor to a remote VNXe/VNX device. It produces a read-only, point-in-time copy ofsource storage data and periodically updates the copy, keeping it consistent withthe source data. The replicated copy can be used in cases where the source data

becomes unavailable such as is a disaster recovery scenario.Note:Replication is not an alternative to keeping point in time snapshots andbackups where you need to access/restore the data at a specific date/time.

Question: Is VNXe replication Synchronous or Asynchronous?

Answer: VNXe replication is Asynchronous. This means that whenever data is written to thesource, it is not instantaneously replicated to the destination. Data is replicatedmanually or based on a certain time interval called Recovery Point Objective(RPO).

Question: What is RPO setting in Replication for VNXe?

Answer: RPO setting in VNXe determines how frequently the destination is updated withsource changes. In other words, RPO is the amount of time between data beingwritten at the source and the same data being written at the destination. It isimportant to understand that is a disaster at the source occurs during this time, anydata written during that timeframe could be lost if the source is unrecoverable. Ifyou anticipate a large rate of change of data on your source, it is recommended todecrease your RPO setting value so that the data is synchronized more often andin smaller chunks.

Question: Does VNXe support One to Many replication?

Answer: No, VNXe does not support One to Many replication. Replication can only be donefrom a source to one destination.

Question: What are the destination platforms supported by VNXe for replication?

Answer: The following are supported:

VNXe to VNXe (Same SP and Different SP)

VNXe to VNX/Celerra (DART 6.0 or above)

VNX/Celerra (DART 6.0 or above) to VNXe



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Question: Can I use Deduplication feature when I replicate?

Answer: Yes, you may use Deduplication feature when you replicate. You have the option ofturning on deduplication on the source prior to replication or turn on dedup of asource that is already replicating. When you turn on dedup on the source side, itwill automatically turn on deduplication on the destination object after the next

synch. You may also note that at this point the destination deduplication will be inan Enabled Suspended state.

You will not be able to force a scan on the destination. However if you failover yoursession your session, you will be able to run a forced deduplication scan in thedestination.

Question: What happens when I turn off deduplication on the source?

Answer: If you turn off deduplication on the source, it will wait until the next synch operationto take place after which the destination deduplication automatically turns off.

Question: If I setup a replication session, do shares get replicated over to thedestination?

Answer: No, shares created on the source will not be replicated to the destination. You willhave to manually create the shares on the destination.

Question: What are the basic internal steps during a replication process?

Answer: VNXe Replication uses internal checkpoints to replicate data. These internalcheckpoints are not available for user management, meaning you cannot performoperations on them such as delete or restore.

Replication process involves the following internal steps (These assume that thereis a connection setup and validated between source and destination devices):



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1. Network clients can read and write to the source without interruptionthroughout the process. Destination is read-only throughout the process.

2. VNXe administrator creates a replication session between the source anddestination objects.

3. The source side establishes a connection to the destination object using theinterfaces specified.

4. Replication creates two checkpoints for the source object.

5. Replication creates two checkpoints for the destination object.

6. Replication verifies that there is no common base established between thesource and destination objects.

7. A full copy is performed to transfer the data on the source object to thedestination object. If the user specifies a manual synchronization option, thedata transfer will occur only when the user performs a manual syncoperation.



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8. At the destination, the first checkpoint ckpt1 is refreshed from thedestination object to establish the common base with the source checkpoint.

9. After the common base is established, the second checkpoint ckpt 2 at thesource is refreshed to establish the difference (delta) between the originalsource checkpoint and the latest point-in-time copy. Only the delta between

the currently marked internal checkpoint and the previously replicatedinternal checkpoint is transferred to the destination by block ID. The transferis called a differential copy.

10. After the data transfer is complete, replication uses the latest internalcheckpoint taken on the destination to establish a new common base ckpt2. The latest internal checkpoint contains the same data as the internalcheckpoint on the source (ckpt 2) that was marked for replication.

11. Replication monitors the RPO value (if set) to determine how frequently thedestination is updated with source changes. Without an RPO setting, theuser can perform an on-demand sync.

Question: As part of the replication, will point in time copies (snapshots) of a filesystem be replicated to the destination?

Answer: Manual or Scheduled snapshots of the source file system will not be replicated tothe destination as part of replication. You may take snapshots on the destinationmanually.

Question: In the case of VMware NFS Datastore Replication, can I use the datastore onthe replicated side (destination) to boot VMs for testing purposes?

Answer: The destination datastore is read-only and this will prevent from booting any VMs.However, in VNXe Operating Environment MR2 or later version, there is an optionfor taking a snapshot of the destination datastore and promoting it. Promoting adatastore will create a writeable checkpoint which can be used for booting the VMs

in that snapshot.

Promoting snaps on the destination application is supported only for VMwareapplications in MR2. Future versions will provide this option for promotingdestination snaps for Shared Folders.

Question: Can I create a schedule to take snapsho ts on the destinationapplication?

Answer: No, you cannot create scheduled snapshots on destination applications. Scheduledsnapshots involve the risk of running out of protection space on the destinationwhich will disable replication. However you can take manual snapshots.

Question: Do I have to provision protection space on the source to enable/start

replication?

Answer: Yes, provisioning protection space on source and destination is mandatory forenabling replication. Replication makes use of internal snapshots which requiresprotection space. When you create a destination application (Shared Folders orVMware NFS), in the second step of the wizard, where it asks you to select asource, it only lists the sources which have protection space provisioned.



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Question: Why do I not see any Windows (CIFS) shares in the destination VNXe afterreplication?

Answer: VNXe only does the data replication from source to destination. Share and sharepermissions are not replicated. Please take a look at Knowledge Base Articleemc276897 available from the search tool on emc.com/vnxesupport for more

details.

Question: How do I find out what are the replication sessions that are on my VNXe?

Answer: In the VNXe GUI, go to System>System Replications. All the replication sessionswill be listed in this screen.

You may also execute svc_storagecheck -replication -sessionsto get a list ofactive sessions.

Question: What are the steps involved in setting up a remote replication to a VNXe?

Answer: The following steps provide guidance in setting up replication between two VNXedevices:

1. On the source VNXe, create a Replication Connection to the destinationVNXe.In the VNXe GUI go to Hosts > Replication Connection. Provide theinformation about the destination VNXe box. This step needs to beexecuted only once for any number of replication sessions from the currentVNXe to the destination VNXe. Skip this step if you already have areplication connection setup to the selected destination VNXe.

2. Create a source resource on the source VNXe (Shared Folder / VMwareNFS).

3. Create a destination resource on the destination VNXe. Use the Create aReplication Destination button to create a destination application. If youchoose to create a resource using Create button, it will not be consideredas a destination object.When creating a destination resource, you will be asked to provide thesource system and source resource to link the new destination resource.

4. Create a replication session between the source resource and destinationresource.

a. Go to the details view of the resource then navigate to ReplicationTab > Configure Replication to a Remote System.

b. Select the Destination System and the Destination storage resource.

c. You may select the source and destination interfaces that are to be

used for replication purposes.

d. You may select the synchronization method (Manual / Automatic).

5. After you have created the replication session, you may do any of thereplication actions like, Sync Now, Failover, Failback, Delete the session,and so on.



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Question: Is there a limit for the total number of replication session on a VNXe?

Answer: Yes, here are the replication session limits for different platforms of VNXe:

VNXe 3100 Single SP: 16

VNXe 3100 Dual SP: 32

VNXe 3300: 64

Question: Can I use a different Ethernet Port than the one used by a Shared Folder forreplication?

Answer: Yes. You may use any of the interfaces available on the source or destination toroute the replication traffic. For example, you may use the interface used by aniSCSI server or a second interface used by the shared folder server to configurethe replication session.

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