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Monday, 9 March 2015

Data Protector Q&A: SmartCache and non-staged restores

SmartCache is used for non-staged restore of files from vmdk files. As such, vms should be first copied to SmartCache and then to StoreOnce. What about if I want to restore files from VMs that are stored only on StoreOnce. Can I copy them to the SmartCache and then use non-staged restore?
- Andrej K

SmartCache devices are the fastest way of performing a Granular Recovery restore.

  • With a SmartCache device the mount operation completes immediately. 
  • With non-SmartCache devices, the virtual machine disk is restored into a staging directory first. 
Since it can take some time to restore a few hundred gigabytes of virtual disk (compared to the length of time it takes to restore one file out of that virtual disk) they can be significant time savings by using a SmartCache device.

You can copy from a non-SmartCache device into a SmartCache device, but you haven't really saved any time -- one way or another, you have just copied the data into an uncompressed folder.

Here's a relevant quote from Planning, Deploying and Installing Data Protector 9:

Backing up to a SmartCache device is very fast, as you would expect for a disk-based backup device. Unfortunately it does no compression or de-duplication so if you are backing up a 40 GB virtual machine, you will need 40 GB for the backup. So it is not really practical storage format for long-term archiving! 

A typical VMware backup for an important virtual machine will use a SmartCache device as its destination. 1 to 2 days later there will be a copy job to put it into StoreOnce storage (while recycling the protection on the SmartCache storage). Perhaps at the weekend, or perhaps after a week or two there will be copy job to take it from StoreOnce and put it on tape.

Less important virtual machines - where it is okay to recover files in a few hours instead of instantly - would probably be backed up to StoreOnce initially, and then copied off to tape without ever using a SmartCache device.

Greg Baker is one of the world's leading experts on HP Data Protector. His consulting services are at He has written numerous books (see on it, and on other topics. His other interests are startup management, applications of automated image and text analysis and niche software development.