TSM Deduplication – Handling of large objects (SPLITLARGEObjects and more)

This information is meant to discuss some useful TSM server parameters in relation to deduplication. It is by no means an in-depth explanation about TSM’s deduplication, or even deduplication in general.

If you have a Virtual Tape Library (VTL) which can (in-line) deduplicate the stored data, e.g. IBM’s ProtecTIER, you most likely want to use this built-in hardware deduplication functionality. As you are aware, you can also choice to use TSM’s native deduplication. This means deduplication on the TSM application level and it is available for client-side and server-side, or even a combination of both.

There might be problems when one is trying to deduplicate very large objects, because this will result in many, many chunks, associated metadata, server processing, etc. Sometimes it might be beneficial to just exclude very large objects from deduplication altogether.

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Partitioned Hybrid Model vs. Cooperative Hybrid Model

TSM4VE – Protecting MS SQL

This (lengthy) article will only focus on MS SQL, but the majority is also applicable to MS Exchange.

During most of my recent TSM for Virtual Environments (in this case Data Protection for VMware) implementations, the following question always comes up:

“Is TSM4VE is capable of backing up an installation of MS SQL that is running inside a virtual machine?” Which can be translated to: “How to protect MS SQL databases hosted in VMware”?

There are a few basic challenges with this:

  • Application consistent backups;
  • Recover individual SQL databases from the backup;
  • Roll-forward SQL logs to a specific point-in-time (PIT).

The chosen method or level of protection required depends on the recovery point objective (RPO):

  • Is a PIT restore to the last full backup sufficient?
  • If not, there is a need to also backup SQL logging. This to be able to roll-forward the database transactions since the last backup after the restore.

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TSM4VE control files (CTL) in a LAN-free enabled environment

The following is post is a guest-post written by Julien Sauvanet. I worked with Julien in the past, and asked him to write a guest post because I think it might be beneficial to the intended audience. The only thing I did was some moderation.

First of all, let’s explain what these CTL files are. When performing a virtual machine backup using TSM4VE, two different pieces of information (seen as files within TSM server database) are sent to the TSM server:

  • .DAT files: are basically the files containing the client’s data being backed up;
  • .CTL files: these are the control files containing information about each DAT file. Each time a .DAT file is sent, there is a .CTL file associated to it, which is stored on the TSM server as well.

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Mimic TSM4VE’s snapshotting in VMware (snapshot quiescing troubleshooting)

Sometimes you might run into a failing TSM4VE backup. In this case, when the creation of a snapshot is not possible. A good place to start is to use VMware’s vSphere software to try to manually create the snapshot.

A common misunderstanding is that sometimes this “direct” VMware snapshot performs just fine and someone thinks that TSM4VE must be the problem. To correctly mimic TSM4VE’s snapshot behavior on the VMware level you need to select the correct options.

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