NDMP Question

The format used by NDMP is NOT in the Spec. It's the only way they got
all the NAS vendors to agree to use it. NDMP is only a communication
protocol. It says "hi. I'm here to back you up, please send a backup
stream to this device." NDMP then does what it's told and tells your
backup app what it sent and where it sent it.

Think of it like a database app. RMAN is a control protocol, not a
format. Your backup app says "hi. I'm here to backup your Oracle
database. Please send a backup stream to there." RMAN then does what
it's told and tells your backup app what it sent and where it sent it.

In neither case does your backup app understand the format of what has
been sent to tape. It does not translate it into it's own format, but
it MAY put some blocks at the beginning and end so that it understands
that it's an NDMP/RMAN image, but it does not translate/encapsulate the
stream itself. In the case of NDMP, it's going to be dump/tar/cpio, or
whatever the filer vendor chose.

Because of that, you CANNOT restore a NetApp NDMP backup to a
Bluearc/Onstor, etc. If you happen to have a Unix box, you can use the
manual and mt to position the tape to the point where the dump starts,
then use dump to read the backup, but you'll lose any Windows ACLs you
had stored in there, as NetApp hacked dump to support ACLs (and all the
other NAS vendors did the same thing).

This is why I recommend NDMP ONLY for backups -- not archives. If
you're going to archive data, it needs to be in a platform-independent
format, and NDMP is not platform-independent. I recommend NDMP only for
backups.

If your backup software supports synthetic full backups, you can read a
blog entry I wrote about an alternative to NDMP:

http://www.backupcentral.com/content/view/48/47/


I hope this helped.

---
W. Curtis Preston
Backup Blog @ www.backupcentral.com
VP Data Protection, GlassHouse Technologies

-----Original Message-----
From:
] On Behalf Of Nik
Simpson
Sent: Tuesday, July 10, 2007 2:34 PM
To:
Subject: [C.A.S.] NDMP Question

From the way I read the spec for NDMP it defines a method for writing
data to tape, not just moving data from tthe NAS too a backup
application. Do backup vendors actually write NDMP daata streams
directly to tape, or do they typically encapsulate in their own
proprietary on tape format?
--
Nik Simpson
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