Remote Blob Storage for SharePoint 2010 with Stepwise – Part 3 Disaster Recovery

This is the third post in this series on Stepwise, Backup and Restore, and Disaster Recovery.

Using Stepwise Remote Blob Storage we have learned that the documents are “externalised” from the SharePoint SQL Server content database and stored on alternate filesystems. One of the interesting side-effects of this externalisation process is the fact that documents are created by Stepwise whenever a file is added to SharePoint, but if the same document is updated in SharePoint a completely new file is created in Stepwise. This happens regardless of whether you have version control turned on in your document library or not – every write to SharePoint results in a new file being created in Stepwise.

The interesting part of this is what happens in a disaster recovery scenerio when you lost your SQL Server content database(s). Because Stepwise has a copy of every single document written to SharePoint, when restoring your data you only need to restore the SQL Server databases. The filesystem that Stepwise is using already has your previous versions of documents on it (up to a point – see Garbage Collection below). This can drastically reduce your restore time.

Furthermore, Stepwise actively collects SharePoint information and metadata as it processes documents. This information is maintained with the document and is accessible to Stepwise administrators. So here’s another nice side-effect of the process – you may have lost 4 hours of SharePoint content database, but Stepwise can determine what files were added in the last 4 hours and provide the metadata and documents for everything that occurred during that 4 hour window. Result – no lost documents!

But what happens if you lose your filesystem, and 4 hours goes up in smoke on that? Obviously that is not a good thing! That is definitely a time to get your restore process started, however again Stepwise can assist in the task. Stepwise still maintains metadata and file information in it’s own database, and it can report back all the documents that were added/changed in the 4 hour window. So while it isn’t all good news, you can at least let clients know exactly what they have lost rather than leave them in the wilderness. And some more good news? Stepwise caches recently accessed documents locally on your web front-ends – including documents that have been uploaded to SharePoint. So we can interrogate the Stepwise cache and pull documents out of there as well.

It’s not perfect – but anything that can help you recover your data after a disaster is a good thing!

What is Garbage Collection?

Remote Blob Storage uses the term Garbage Collection to describe the clean-up process of deleting documents that are no longer being referenced. As an example, consider a document that has been deleted from a document library in SharePoint. It first hits the user recycle bin, then the site collection recycle bin, then finalled the deleted from end user recycle bin. After it leaves this area, SharePoint no longer maintains any connection to the document.

It is at this stage that the Garbage Collection process in Stepwise kicks in. Stepwise uses the Remote Blob Storage API to identify any documents that SharePoint no longer references. It then checks a configurable number of days parameter (defaults to 7 days) and if the date is older than this, it will physically delete the document from the back-end storage.

In some situations, such as WORM-based configurations of Stepwise and/or for compliance reason, Garbage Collection can be disabled completely. This ensures that all documents are maintained by the system indefinitely.



One Response to “Remote Blob Storage for SharePoint 2010 with Stepwise – Part 3 Disaster Recovery”

  1. Remote Blob Storage for SharePoint 2010 with Stepwise – Part 2 Backup and Restore « Back in Hack Says:

    […] on it. « Remote Blob Storage for SharePoint 2010 with Stepwise – Part 1 Remote Blob Storage for SharePoint 2010 with Stepwise – Part 3 Disaster Recovery […]

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