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please clarify VERITAS NetBackup is stub aware?and how it works

There is a project to start migrating COLD data off the ISILON Production cluster “server1” to ECS Storage. Post migration of COLD data, stubs or pointers are left behind on the ISILON production storage

Can you please clarify VERITAS NetBackup is stub aware?and how it works, is it required any special license to use this feature.




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Re: please clarify VERITAS NetBackup is stub aware?and how it works

You haven't mentioned file-system type or presention, so I assume NTFS "like" via SMB is the native presentation to end users.  And you haven't mentioned backup method, so I assume backup via NetBackup is via NDMP.

And you haven't mentioned versions of anything.  Sighs.

No special license required for NetBackup to access "stubs".  Assuming you have licenses to backup the Isilon already in whatever way you do.

Personally I haven't looked in to this for some time, but a few years ago when we were deploying Veritas Enterprise Vault we found that NetBackup was able to backup SAN based (appeared as local) NTFS volumes and secure stubs without recalling content and was able to restore stubs, and the stubs still worked after restore.

You haven't mentioned the software/platform which will perform the stubbing, but my prior understanding was that the ability for the file-system to recall previously offlined/stubbed content was embedded within the Windows OS at the file-system driver layer, i.e. NetBackup from a file-system walking agent is to all intents and purposes unaware, and just sees short files of less than 4KB - but this would only be relevant for file-system based backups.

But I would expect that if your backups are via NDMP then you should have even less to worry about, because NDMP is not NetBackup reading the Isilon, NDMP is the Isilon sending its proprietary binary file-system stream to NetBackup and so if NDMP backups are used then there is no danger of content being recalled from ECS, and so restores should not be a problem either.

Time for a PoC to prove it to yourself?

Re: please clarify VERITAS NetBackup is stub aware?and how it works

In most cases, a stub is just a shotcut. NetBackup doesn't care what it is, it's just a file for all it cares. We backup Enterprise Vault "stubs" or "placeholders" without any issue, but that is not because of any special integration, it's because the "stub" is just a file with information inserted into the Alternate Data Stream of the file.

As SDO stated, you might want to give more information when posting your question i.e. what is archiving (migrating) these files?

Re: please clarify VERITAS NetBackup is stub aware?and how it works

NetBackup itself is not stub aware, nor are most/any other backup products.

If a backup client is going to walk / backup a file system containing stubbed files, then one has to instruct the "archiving agent" / "stub recaller" to ignore read requests generated by said backup product.

e.g. the Enterprise Vault "FSA" (File System Agent) needs to be instructed to ignore (i.e. not recall content) when "bpbkar32" accesses stubbed files :


And, I did find a similar article for a different archiving product - so it would seem that they have similar methods, i.e. that the "stub" layer needs to be told which processes to ignore.

And so you would also have to add your A/V process to the list of process to ignore.


But, all of the above is for file-system based directory tree walking file reading style of backups - and so all of the above is irrelevant if you are doing NDMP style backups.