TSM Copy pool or Isilon SyncIQ to create a copy of your backup data ?

 

If you follow this blog you are aware that many customers use Isilon Scale Out NAS as a backup target for TSM. In this context I am getting asked quite frequently whether to use Isilon’s SyncIQ or TSM Copy pools to replicate your backup data. The response to that is clear: use TSM Copy Pools. Here are the reasons:

1. SyncIQ is a parallel replication that is designed to replicate massive amount of data. It works is parallel from multiple nodes to multiple nodes at the target side. Due to the nature of a scale out NAS system it’s designed to replicate the data asynchronously (otherwise your response time on the primary side would suffer). Assume your primary site would go down due to a power outage. Transactions will not be lost due to the non-volatile NVRAM buffer that OneFS uses to store transactions. However, if you failover your cluster to the secondary side, OneFS would rollback the target directory to the last known good snapshot. That has two consequences:
   

   a.) Even if you have set the RPO to some minutes, you will lose the backup data that has been written between the last snapshot and the occurrence of the power outage (if you cannot recover your primaries site volume).
   
   b.) TSM will recognize it and would report inconsistencies between the database and the volume in the log. This might not be a disaster but you would then need to perform an AUDIT VOLUME which checks for inconsistencies between database information and a storage pool volume. This can take quite a long time !

2. The second reason why you would use TSM Copy Pools to duplicate your data is that TSM uses it intelligently in case you need to restore data in a quite utilized environment. Since TSM is aware of it’s (synchronous) Copy Pool Volume, it would mount it and use it in addition to the primary volume to restore data.
   

A final comment on disaster recovery for TSM. The above topic discusses how to make you backup data highly available but not the TSM server itself. Take a look at the General Storage Cluster Controller for TSM. It is a backup recovery solution that allows to create a highly available solution for TSM. It even covers the outage of TSM servers and works perfectly with Storage Pool Volumes on Isilon.

Resources:

[1]  White Paper: High Availability and Data Protection with EMC Isilon Scale-Out NAS
[2]  TSM Info Center: AUDIT VOLUME (Verify database information for a storage pool volume)
[3]  General Storage Cluster Controller for TSM: Brochure