Frequently Asked Questions on NetBackup Accelerator

Protection ‎07-03-2012

NetBackup Accelerator is an exciting feature introduced in NetBackup 7.5 and NetBackup Appliances software version 2.5. This blog is not a substitute for NetBackup documentation. NetBackup Accelerator transforms the way organizations do backups, I am compiling a list of frequently asked questions from NetBackup Community forums and providing answers. If you have follow up questions or feedback, post them as comments. I shall try to answer the questions or someone else in the community can jump in. Fasten your seat belts! You are about to get accelerated! 

What is NetBackup Accelerator?

NetBackup Accelerator provides full backups for the cost of an incremental backup.

cost reduction in full backups = reduction in backup window, backup storage, client CPU, client memory, Client disk I/O, network bandwidth etc.

NetBackup Accelerator makes this possible by making use of a platform and file system independent track log to intelligently (there are a number of intellectual properties associated with this technology) detect changed files and send the changed segments from those files to media server. These changed segments are written to a supported storage pool (currently available only in NetBackup appliances, NetBackup Media Server Deduplication Pools and PureDisk Deduplication Option Pools) and an inline optimized synthetic backup is generated.

What is NetBackup Accelerator track log?

Track log is a platform and file system independent change tracking log used by NetBackup Accelerator. Unlike file system specific change journals (e.g. Windows NTFS change journal), there are no kernel level drivers that runs all the time on production clients. The track log comes to action during the backup and is populated with entries that are used by NetBackup Accelerator to intelligently identify changed files and segments within the changed files.

The size of the track log is a function of number of files and size of the files in the file system. The size of the track log does not increase with increase in data change rate in the file system.

So, NetBackup Accelerator is good for full backups. How about incremental backups?

The primary benefit from NetBackup Accelerator is for full backups. However, NetBackup Accelerator also reduces a subset of costs in running incremental backups. 

cost reduction in incremental backups = reduction in client CPU, client memory, Client disk I/O 

Since I can get full backups for the cost of doing an incremental backup, should I simply delete my incremental schedules and increase the frequency of full backups? 

Not recommended unless you are not concerned about the catalog growth. Note that full backups will have catalog files (the "*.f" files in NetBackup image database) larger than those of incremental backups. Running full backups instead of current incremental backups would mean that your image catalog size would increase. Larger catalog requires more space on your master server and it takes longer to run catalog backups. 

As I mentioned in the answer to the previous question, NetBackup Accelerator does help with incremental backups as well by significantly reducing the impact of backups on client's resources. Stick with your current schedules and take advantage of NetBackup Accelerator. 

What is NetBackup Client Side Deduplication?

NetBackup Client Side Deduplication deduplicates data and sends unique segments directly to storage server. Media server is not involved in this data path. For example, if your storage target is a NetBackup 5020 appliance sitting behind a media server, the NetBackup client is sending the unique segments directly to NetBackup 5020 appliance. This design makes it possible for a media server to support many storage pools and clients (scale-out on front-end as well as on back-end).

If your storage pool is media server deduplication pool (MSDP) or a NetBackup 52xx appliance, the storage server and media server co-exist on the same physical system. Even in this case, NetBackup Client Side Deduplication is sending unique segments directly to storage server (which just happened to be a media server as well) and hence you get both front-end and backend-end scale out. For example, it is possible to have a NetBackup 5220 to host a media server deduplication pool while also serving as a media server for another NetBackup appliance or media server. 

What is NetBackup Optimized Synthetic Backup?

NetBackup Optimized Synthetic Backup is a feature where a full backup can be synthesized on storage server by making use of previous full and subsequent incremental backups without reading those component images and writing a new image. This technology had been in NetBackup since 6.5.4. It is available on all NetBackup appliances, Media Server Deduplication Pool and PureDisk Deduplication Option Pool. Recently some of the OpenStorage partners have also announced support for this feature.

Can you compare and contrast NetBackup Accelerator and NetBackup Optimized Synthetic backup?

NetBackup Accelerator provides all the values you get from NetBackup Optimized Synthetic backup and a lot more. In fact, if you have a supported storage pool for NetBackup Accelerator, there is really no need for you to use NetBackup Optimized Synthetic backup.

NetBackup Optimized Synthetic backup is a post-backup synthesis. You need a separate schedule that generates synthetic backup after incremental backups are done.  NetBackup Accelerator generates the full backup inline when data is being sent from client.

NetBackup Optimized Synthetic backup requires you to run traditional incremental backups. Hence all the limitations of a traditional incremental backup are applicable. For example, the incremental backups do require NetBackup client to enumerate the entire file system to identify the changes. NetBackup Accelerator makes it possible to intelligently identify changes and read just the changed files.

I can list a lot more, but you get the point by now. Bottom line is… if your storage pool supports NetBackup Accelerator, there is no need to use the older NetBackup Optimized Synthetic backup schedules.

Can NetBackup Accelerator and NetBackup Client Side Deduplication co-exist?

Of course! In fact, these two features are like milk and cookies. They are tasty by themselves but delicious when eaten together!

NetBackup Accelerator reduces the cost of doing a full backup (see the question “What is NetBackup Accelerator?”  for the definition of the cost). When you combine it with NetBackup Client Side Deduplication, some of the advantages are…

  • Global deduplication without deduplication processing penalty on client. For our competitors, turning on source side deduplication would imply resource consumption on production client system to support dedupe fingerprinting. Because of NetBackup Accelerator, the resources needed on client are significantly lowered in NetBackup. In fact, it is fair to say that NetBackup Accelerator lets you dedupe at source confidently. 
  • Ability to directly write to storage server. If client side deduplication is not enabled, Accelerator sends changed segments to media server first. With client side deduplication enabled, the changed segments are directly sent to storage. The result is scalability (front-end and back-end scale-out). A media server can support 100s of clients and 10s of storage pools.
  • Support for in-flight encryption and compression (configurable at pd.conf on clients)
  • No incremental licensing cost. Both Accelerator and NetBackup Deduplication are on the same SKU. You already have both capabilities if you paid for one or the other.  Turning on/off these features are at the click of a mouse, try it anyway! 

Are they any workloads where NetBackup Accelerator cannot be used?

The graphical user interface is designed to grey-out enable accelerator check-box for the policy types where NetBackup Accelerator is currently not supported. Furthermore, if you happen to choose a storage unit that does not support NetBackup Accelerator, the policy validation is designed to fail when you try to save changes to the policy.

Are there any design considerations when not to use NetBackup Accelerator when NetBackup Client Side Deduplication is used? 

No! NetBackup Accelerator does not have any negative effects on NetBackup Client Side Deduplication.

Are there any design considerations when not to use Client Side Deduplication when NetBackup Accelerator is used? 

No functional limitations.  But there are a couple of situations where you do not get the advantage of NetBackup Client Side Deduplication at this time.  The good news is that there is nothing you need to do during the design or implementation.  NetBackup knows not to attempt NetBackup Client Side deduplication in these scenarios. I am listing them for the sake of awareness.

  • Remember is that NetBackup Client Side Deduplication is available for a subset of NetBackup Client platforms. Refer to NetBackup Deduplication documentation for more info. NetBackup Accelerator is available for ALL supported client platforms with the exception of OpenVMS.
  • If your storage pool is NetBackup Cloud (to Nirvanix, AT&T Synaptec, RackSpace, Amazon etc.), NetBackup Client Side Deduplication is not currently available. NetBackup Accelerator is supported. 

Note: Thank you for so many follow up questions! I have made sincere attempts to answer all of them down below. Furthermore, I would like to bring your attention to two additional blogs you may be interested in