NetBackup header information

[Michael_Zhu]

Does anyone know the exact NetBackup header information? I am using NetBackup 5.1 on a Windows 2000 server. At the time I label the tape, NetBackup sends down a 1024 bytes write. I think this 1024 bytes is the NetBackup header. As to my observation the format of this 1024-byte looks like the following.

VOL1XXXXXX...........
.....................
.
.
.
.....ThIs Is A BP tApE hEaDer
.......................
..
..
..

In this header "XXXXXX" represents the 6-character media ID rather than the exact BarCode. For example if the BarCode is 01450000, then the media ID is 450000. It seems that the media ID is always 6 characters long. Is this the truth for NetBackup? Also I couldn't find the exact BarCode in the header.

"ThIs Is A BP tApE hEaDer" is specific to NetBackup? What is the exact meaning of this string? Is this string a flag for this NetBackup header?

Does anyone know the exact data format of this 1024 bytes?

Thanks.

[Stumpr2]

There is an example of the header in the technote:
How to read a tape header to verify the recorded volume serial number
http://seer.support.veritas.com/docs/232409.htm

Which of the six characters on the barcode that should be used can be defined in the vm.conf file.

ThIs Is A BP tApE hEaDer tells netbackup that it is a netbackup data tape as opposed to a catalog tape or from another system and NOT a netbackup tape.

If you want to do just a quick reading of the header and not a dump then you could use:
# bpmedialist -mheader -m 600011
media id = 600011, allocated 09/14/2005 21:13, retention level = 6

I'm sorry but I do not know the exact breakout of all the fields for the header dump. Perhaps Jeffrey Redington may have that info.Message was edited by:
Bob Stump

[MayurS]

if your barcode is 8 characters long then netbackup will read it from right -> left 6 characters.
If you want that Ntebackup should include the first Six characters from Left -> Right then
in /VOLMGR/VM.conf we have to putin this entries

MEDIA_ID_BARCODE_CHARS 0 8 1:2:3:4:5:6

If a barcode is ABC001L1 if the barcode is read by NB as C001L1
then the above entry will read the label as ABC001Message was edited by:
Mayur Shinde

[Michael_Zhu]

Thanks, Bob and Mayur.

Bob, if NetBackup sends down a 1024 bytes write which contains the "VOL1XXXXXX..............ThIs Is A BP tApE hEaDer" info, does this mean that NetBackup wants to write its header on the tape? In other words does this mean that this 1024 bytes write comes from NetBackup rather than from any other backup utility? And this NetBackup header is always 1024 bytes long?

Bob or Mayur, the NetBackup media ID has to be 6 characters? Is there a way to get the exact barcode back from a NetBackup tape?

Thanks.

[Stumpr2]

NetBackup will mount the tape that it has selected for writing. It then attempt to read a header (label) if it exists to determine the purpose of the tape. The tape header could contain tar, ansi, cpio, mtf1 etc... If it does then NetBackup will freeze the tape and not use it unless the media server has been setup to overwrite other media types. If a label exists that identifies the tape as a netbackup catalog tape then NetBackup will not write to the tape. If NetBackup discovers a normal NetBackup label exists then it will continue the backup process and position to the last EOF and write the new backup image onto the tape. If there is no label (virgib tape) then NetBackup will create (write) a new label unto the tape.

1024 is not necessarily the byte format. This is discussed in the technote for which I provided the link.

MediaManager TL8 and TLD robot types now support barcode lengths of up to 16 characters. There is more information available in the "Media Manager Admin Guide"Message was edited by:
Bob Stump

[MayurS]

HI,

Refer to this document also
http://seer.support.veritas.com/docs/275633.htm

Let us know your existing External media ID and how netbackup reads it...and what do you desire the Netbackup to read the ID as.

[MayurS]

If your Barcode is 01450000
and u want NB to read it as 014500 then in VM.conf add the below entry and restart the media manager service and re-introduce the tape to your library.

MEDIA_ID_BARCODE_CHARS 0 8 1:2:3:4:5:6

If you want the media id to be read as 01450000 it self update the VM.conf as probably

MEDIA_ID_BARCODE_CHARS 0 8 1:2:3:4:5:6:7:8
;)

[Jeffrey_Redingt]

Not only does NetBackup want to write a header to tape but it has to write a header to the tape in order to write to the tape. The 1024 byte header is NetBackup specific and as has been described contains the tape label and the words "this is a bp tape header". The rest of the header information is filler to create the 1024 byte header file. This particular header is specific to NetBackup but other backup products also write headers to the tape. Some are 1024 bytes and others aren't. It varies by vendor. The NetBackup header is and should always be 1024 bytes. The NetBackup media ID is always 6 characters. The media id can be adjusted to read any of the 8 character bar code labels that are on the market if your barcode reader supports it and you can choose which of the characters will be used for the media id as described by Bob and Mayur. It will never write the entire 8 character barcode into the header. I am not sure why you would need to. Based on the 6 characters you should be able to identify any piece of media based on the header.

[Michael_Zhu]

Bob, Mayur and Jeffrey, thank you very much for the valuable information.

Mayur, I tried your suggestion. I defined "MEDIA_ID_BARCODE_CHARS = 0 8 1:2:3:4:5:6:7:8" in the vm.conf file, restarted the media manager service, deleted all the old volumes and re-introduced the tapes. But the media manager just selected the first 6 characters of the barcode as the media ID. A media ID generation rule only consists of a maximum of six fields, just like Jeffrey mentioned in his message.

Jeffrey, the reason I need this NetBackup header information is that I want to implement a tape identification module which can recognize different kinds of tapes, such as IBM Tivoli, Legato, Veritas Backup Exec and NetBackup. So can you provide me with more detailed information about this 1024 bytes NetBackup header? I mean the exact data structure.

Thanks all you guys again.

[MayurS]

Ya i tried at my end; Nb will not take media id greater than 6 characters.....

[Michael_Zhu]

Thanks, Mayur, your information is very helpful.

[MayurS]

HI Michael,

isn't your problem resolved. This post still shows as NOT ANSWERED

[Michael_Zhu]

Mayur,

Yes, my question has been answered. I just hope that Jeffrey can give me more detailed info about the exact format of the 1024 bytes NetBackup header.

Anyway, thanks all of you guys.

[Jeffrey_Redingt]

Unfortunately, I can't give you any more exact information than is in the technote and what I have told you. Every NetBackup header will be 1024 chars and will contain media id and This is a bp tape. Everything else is padding with 0's to make sure the header is 1024 chars. I wish I could be more specific like 18 bits in you will find the media id but I can't. Sorry.

[Michael_Zhu]

Hi, Jeffrey, you already give me a very big help. Thank you. One more question. The words "ThIs Is A BP tApE hEaDer" is specific for NetBackup data tape? What is the different between NetBackup data and catalog tape? Does NetBackup catalog tape also contain similiar header?

Thanks.

[Stumpr2]

The catalog header is similar in construction but it is different. It is one of the items that NetBackup checks when it mounts the tape. NetBackup reads the header and will not allow the use of a tape that contains a catalog header to be written to as a regular data tape. The only way to reuse a previously used catalog tape as a data tape is to relabel it. That will cause it to rewrite the catalog header with a data tape header.

[Jeffrey_Redingt]

Yes, all NetBackup tapes contain that statement regardless of whether they are a data or a catalog tape.