Networker

Re: [Networker] Delete data from tape?

2008-04-30 14:47:08
Subject: Re: [Networker] Delete data from tape?
From: Tim Mooney <Tim.Mooney AT NDSU DOT EDU>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Wed, 30 Apr 2008 13:40:51 -0500
In regard to: [Networker] Delete data from tape?, cmt2008 said (at 12:41pm...:

Could Networker delete the specific backup data from tape manually?  Or
it should be waiting for the expiration date?

I'm not sure what you're asking, but be advised that even if NetWorker
expires a particular saveset or volume, or you force NetWorker to forget
that a particular saveset is on a particular volume (which you can do,
using nsrmm), the data is still on tape.  It's not "deleted from tape",
and if you're familiar with NetWorker and know what you're doing, it's
possible to recover that data.

Once NetWorker recycles a volume (which writes an updated label to the
beginning of the volume), it becomes very very difficult for most people
to get at the previous data that is on the tape.  This is because of the
way nearly all modern tape drives work.  When you write a file to a tape
drive and the write completes, the tape drive writes an "end of tape" or
"end of media" sequence (generally it's just two "end of file" markers in
a row) to the tape.

If you think about this for a while, you'll come to the realization that
any write to a tape drive makes it very difficult (for the average IT
person using standard tools) to get to any data that may have been on
the tape at a later position.  Once a write completes and an EOT marker
goes down, it's a major challenge to get at data later on the tape.

Even in that situation, though, the data is still there, and people with
the will to get at it and the appropriate tools definitely can.

Sorry for the long digression, but I wanted to make certain you understood
that the act of making NetWorker forget about a saveset does NOT delete
the data from tape, it just makes NetWorker forget that the data is there.
That's an extremely important distinction, especially when you start
talking about things like complying with a subpoena or various
data-handling laws or policies.

Tim
--
Tim Mooney                                        Tim.Mooney AT ndsu DOT edu
Information Technology Services                   (701) 231-1076 (Voice)
Room 242-J6, IACC Building                        (701) 231-8541 (Fax)
North Dakota State University, Fargo, ND 58105-5164

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