Overview

As a review, the open storage option, referred to by Symantec as OST (OpenStorage), is an API that Symantec created for writing to disk. When NetBackup or Backup Exec wants to send a job to disk, it uses the API to tell the storage device  that it has a backup for it to store, and it gives that backup a name. The storage device then accepts the backup and stores it in a manner of its choosing.

 

After that, NBU can do one of three things with the backup set:

 

• Expire it
• Restore from it
• Copy/duplicate it

If NetBackup or Backup Exec tells the storage device (via the API) to expire the image, the image is supposed to be deleted from storage. When NetBackup or Backup Exec wants to restore from an image, it uses the API to tell the storage device what image it wants to restore from. The storage device then delivers the image to NetBackup or Backup Exec for restore. (Again, both of these are very similar to the way that RMAN talks to backup apps.)

 

The really powerful part of OST comes into play when NetBackup or Backup Exec wants to duplicate a backup. OST supports what it calls optimized duplication, as shown below.

 

 

 

 

For this to work, you need to have previously registered two OST-capable storage devices from the same vendor. NetBackup or Backup Exec then tells Device A (a DXi system) to perform an “optimized duplication” to Device B (a second DXi system). The two devices then communicate and figure out which new data segments have to be replicated from Device A to Device B to properly duplicate the image. 

 

Note:The number of segments replicated will vary greatly, based on deduplication factors, and on how unique this image is, in comparison to previous images already stored on the target device.

 

When the optimized duplication completes, it reports this to NetBackup or Backup Exec through the API, and all of this shows up in the Activity Monitor. If there are problems with the copy, the storage device can report that through the API as well, and the problems will be reflected in the Activity Monitor.

 

When the job completes successfully, NetBackup or Backup Exec will now know about both copies of the image. You can then connect a media server to the replicated Device B and can use those images just like you would any other images, which includes copying those images to tape.
 

---

Facts

The OST replication method ….

• Does not require a replication license and does not require any setup on the source or target
• Can allow replication from any source to any target 
• Is not set up to do continuous replication of a storage server 
• Can co-exist with other replication methods (but not on the same share!!!)
• Allows a maximum of 8 simultaneous replication streams (default setting is 2) due to resource limitations such as memory and network bandwidth

NBU always replicates the full backup image file.

---

 

 

 Go back to the start of the topic >  OST Issues