Kurt: This violates two "rules" for good backup policy.
1. Don't muck with good data. The data on tape is presumably good. Reading it all in and then writing it all back out again are two more opportunities for entropy (and Murphy ) to get at your data. 2. As Gene can probably attest to, tape heads have limited lifespans compared to the rest of your computers. At my last job, we had 4mm DAT drives and did daily backups on our servers. On the average, our tape drives lasted, on average, 14-18 months before failing. Your procedure would shorten the lifespans of similar drives by at least half. To paraphrase an earlier statement, tapes are cheap compared the cost of losing data and the labor to restore it. Buy more tape, that's a better use of your time and money. Best wishes for a Happy New Year. Donald L. (Don) Ritchey E-mail: [EMAIL PROTECTED] -----Original Message----- From: Kurt Yoder [mailto:[EMAIL PROTECTED] Sent: Tuesday, December 30, 2003 7:44 AM To: [EMAIL PROTECTED] Cc: Andrew Hall; Joshua Baker-LePain; [EMAIL PROTECTED] Subject: Re: Append to active tape Gene Heskett said: <snipped> > The design decision is because amanda has absolutely no guarantee > that > someone will not eject the tape, or otherwise mess with the tapes > position, from one days run to the next. So amanda is designed to > do > 2 things: > > 1: rewind the tape and read the label to make sure its the right > tape > in the sequence to use next, doing this with each days invocation. > This in itself destroys the location you get from an 'mt -f device > tell' between last nights run and tonights. > > 2. Because not all tape drives can reliably do an 'mt -f device > seof' > to restore that location, and it would be a total loss to write over > last nights backup with tonights, the chance of doing that is never > taken. Hence, amanda will never attempt to append to a tape. It > *must* know that it has the tapes undivided attention during the > duration of a run. To that end, if the drive has a door lock > command > or ioctl, it is used to prevent you from ejecting the tape in > mid-run. > > Its inconvienient for some, but infinitly safer for all this way. Couldn't "append to tape" be simulated? That is, rewind the tape and check the tape label as normal. Then copy all contents of the tape to the holding disk. Then use amdump to add to the holding disk. Then flush the holding disk back to tape. The drawback to this solution is that it would take quite a bit longer. However, there would be no risk of accidentally overwriting portions of the tape. I'm just asking in theory; I have no plans to implement anything like this at my site. -- Kurt Yoder Sport & Health network administrator ************************************************************************ This e-mail and any of its attachments may contain Exelon Corporation proprietary information, which is privileged, confidential, or subject to copyright belonging to the Exelon Corporation family of Companies. This e-mail is intended solely for the use of the individual or entity to which it is addressed. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution, copying, or action taken in relation to the contents of and attachments to this e-mail is strictly prohibited and may be unlawful. If you have received this e-mail in error, please notify the sender immediately and permanently delete the original and any copy of this e-mail and any printout. Thank You. ************************************************************************
