SnapMirror & SnapManage integrationr

[polani]

Guys

We are going to purchase Netapps storage boxes and snapmirror for our DR solution...however vendor is saying that you have to have snapmanager as well for snapmirror to work effeciently...

We do have sql and exchange on production site and also want to replicate them to Dr site ..however we do have TSM based backup solution in place ( all windows servers have local drives now)...

Question is :

1. Can Snapmirror work without snapmanager for sql and exchange ?

2. Can we use dark fiber ( which is already in place ) to use snapmirror or only TCPIP connectivity required between two sites ?

3. Is there any tool available to size network bandwidth for snapmirror based replication?


4. We do have SUSE server 10 hosts as well. Does Suse 10 supports iSCSI or we should go for NFS protocol on netapps?


Here comes polani Once again!!!

P690 Certified Specailist
HACMP & AIX Certified Specailist
AIX & HACCMP Instructor

 

[RMGBELGIUM]

1. It can work without the snapmanager suite BUT:
The snapmanager places your application (SQL or Exchange) into hot backup mode, and ensures consistency of your databases.It is advised to use this software suite for backups, and do a snapmirror transfer of your backups towards the remote DR box after the backup (can be triggered from within the application ).For the transaction logs, you can do a more frequent snapmirror transfer to minimize dataloss.
2.Snapmirror is based upon TCPIP, but there is a possibility to use IP over fiberchannel.But this needs to be configured again.Most commonly used is snapmirror over TCP/IP
3.There is no tool, but if you can calculate your daily change rate of data,you can calculate the bandwidth needed
Have a look at this page :

http://www.ibeast.com/content/tools/band-calc.asp

Very usefull to determine what line speed you will need if you know your backup window and amount of data to send over.
4.I would advise to try out nfs, as you do not have to take into account any supportability matrix for NFS, as with iscsi you will have to be compliant with ontap version,clustering,hba firmware,hba type,..., and NFS offers good performance nowadays

rgds,

R.

 

[polani]

Hi R,


First of all many thanks for your help and responses...


Infact my concern is more about data consistency with sql or Exchange itself. It seems that Snapmirror creates a baseline of source volume initially ( on target NAS) and then transfer the incremental data on block level from source to target NAS.

Question is how data consistency can be ensured , if sql ( or db2 or exchange ) is running while creation of initial source mirror on NAS?

Can snap manager help in this regard? I am not able to see any document which says that snapmanager is mandatory for snapmirror?


Here comes polani Once again!!!

P690 Certified Specailist
HACMP & AIX Certified Specailist
AIX & HACCMP Instructor

 

[RMGBELGIUM]

The baseline transfer is based upon a snapshot,so you have a consistent point.The only way to garantee application consistency is to shutdown the sql or exchange or place it into hot backup, to be sure that the baseline is 100 pct consistent.You then start the baseline, after which you can restart the applications.Snapmanager cannot help during baseline transfer.Most common scenario is that you set up the baseline transfer , and when the transfer completes you take a snapmanager backup and transfer the changed blocks through snapmirror.At this point in time you will have an application constistent target volume.

 

[xmsre]

The snapmanager suite calls the VSS writer for the application to quiece the IO before calling the Netapp Hardware VSS provider to take the snapshot. Because it is a VSS snapshot and the Writer was called, the snapshot is consistent. Snapmanager initates the snapmirror transfer of the changed blocks in the snapshot after completion of the snapshot as well.

For SME (Exchange), Snapmanager:

1. Calls the Exchange VSS Writer to prepare the database for a snapshot (Freeze).
2. Calls the Netapp VSS provider to take the snapshot.
3. Calls the VSS writer to resume IO (thaw)
4. Archives the log files.
5. Checks the consistency of each DB page and each log file using either an eseutil instance or chksgfiles depending on the exchange version.
5. Initates the Snapmirror transfer (if you specify)

Because this is a VSS snapshot, and the writer was called which put the db in a consistent state, the data in the snapshot is cosistent. Snapmirror works by replicating snapshots, and the snapshot was consistent. That's a huge difference from other replication methods that simply preserve write order and replicate writes as they occur. With that type of replication, there would be no way to tell if the data was consistent or not.

By replicationg snapshots, snapmirror data is always consistent as long as replication completes. If the replication does not complete, then the last snapshot to complete replication is consistent. Consider a schedule for exchange where the database and logs snapped every 4 hours, and in addition, the logs only are snapped every 15 minutes.

At 12:00 database and logs are snapped
At 12:05 the snapmirror completes
At 12:15 the logs are snapped
at 12:17 the snapmirror completes
at 12:30 the logs are snapped
at 12:31 a failure occures.

You are consistent for the last update of the logs at 12:15. For SME, when you use the Business continuance module to execute a business continuance plan in the DR site after the failure, it will restore the 12:00 backup and roll the logs forward to 12:15. Your RPO is the interval of the log updates plus the transfer time. In this example that's 17 minutes maximum.

 

[polani]

Hi xmsre,

many thanks for your response and help

Now it again confuses things ... from your response , it seems that snapmanager for sql and exchange is required to work snapmirror with full data consistency?

My Question still remains same & simple


1. If snapmanager is not used , whether snapmirror will be able to ensure data consistency in case of sql & exchange ?

If yes, then we have to put sql and exchange in quisce mode manually, before each snapmirror process is initiated , am i right in understanding ?

Regards


Here comes polani Once again!!!

P690 Certified Specailist
HACMP & AIX Certified Specailist
AIX & HACCMP Instructor

 

[xmsre]

It's not required, but it works a lot better if you you use it. If you do use snapmanager, you can leverage VSS to quiesce the data for the snapshot to ensure consistency. VSS has three parts; the writer (built into the application), the provider (the piece that actually does the snapshot), and the requestor (the piece that coordinates the activities - in this case SME). If you don't use SME, you'd need another way to quiesce the data before the snapshot. That could get ugly in a hurry.