BW on HANA with Dynamic Tiering and Storage Replication

[Former Member]

Hi Experts,

Here is a question on the HANA TDI

For a new landscape of SAP BW on HANA with Dynamic Tiering we are looking to understand the appropriate Disaster recovery solution

As HANA System replication is not supported for Dynamic Tiering at this point (as of SPS09/SPS10) we would like to know if Storage Replication would be viable solution

Are there any customers currently using such a solution? Have not found any documentation in my search so it would be useful to have any pointers on this topic

Sunil

[Former Member]

Hi Sunil,

Here are my two cents:

Starting points of this case are:

BW on HANA with DT and HADR

RPO = RTO = 24 hours

HW-Provider = Cisco

With DT data on the cold store (in IQ) remains unchanged during the month/year.

Once per month/year a batch process copies older data from the warm store in HANA to IQ and then deletes this data from HANA.

SAP will support system replication for BW on HANA with DT but not before HANA SPS13 (End of 2016 or later). Until that time only the following risk must be mitigated:

Only during the above mentioned batch process an inconsistency can occur. When HANA crashes at the moment when the batch process is writing data to IQ but has not yet deleted this data from HANA. After restarting HANA, the data would be available in both systems. The solution for this inconsistency should be that the batch process should correct the situation by overwriting the older data in IQ and then deleting them from HANA.

Given the above, Cisco's storage replication of the warm store on HANA and of the the cold store on IQ safeguards data consistency. On top of that, making a system backup before and after the batch process of the cold store will guarantee data consistency if you don't trust the batch process and cannot live with the same old data on two stores in case of a crash.

Please note that this solution would not work for Suite on HANA because SoH tables with older data on the cold store can be updated during the month.

Regards,

Lou.

[Former Member]

Thank you Lou for the response

I have been checking for any available documentation on support of Disaster recovery based on Storage Replication for Dynamic Tiering

The below SAP Note for Dynamic Tiering  does have a section for the list of unsupported functionality and Storage Replication is not listed here(we do have a mention of System Replication not supported as you confirmed earlier in this post)

http://service.sap.com/sap/support/notes/2140959

Your explanation above suggests SAP is cautioning the customers using Dynamic Tiering with Storage Replication due to the possible inconsistency that may occur

Could you please point us to an official statement from SAP if Dynamic Tiering with Storage Replication support

Sunil

[lbreddemann]

Technically speaking there are currently (SPS10) only two options available to secure your data here:

Backups and Storage replication.

If the later is the right approach for you of course needs to be evaluated.

One thing to consider here certainly is that the data in the 'warm' (in TDI) layer might have to fulfil different requirements in terms of availability than the 'hot' data. And that can be leveraged when deciding on the data recovery strategy.

- Lars

[Former Member]

Thank you Lars

Good to hear there are no concerns on using Storage Replication as a Disaster Recovery solution for BW on HANA with Dynamic Tiering

Regarding your comment on the availability of the WARM layer compared to the HOT data: when using DT we cannot use 2 different DR solutions for HOT and WARM Data right? Both have to use the same Disaster Recovery  solution for a consistent recovery in case of a Disaster...

Your thoughts are much appreciated...

Sunil

[lbreddemann]

Got me ... hehehe ...

i was thinking along the following lines:

If the system replication would cover the HOT data part (the core SAP HANA data) and it wouldn't be required to have the DT part included in that, then one could say:

well, we just recover the DT part manually after the fail over.

Until this is done the DT data would just not be available. (*)

But thinking about it, I figure that this is not even supported...

So, storage replication and classic database backups are the only real scenarios here.

(*) if instead of DT a standalone IQ via SDA would be used, this scenario would be possible IMHO.