On Monday 07 May 2007, Donofrio, Lewis wrote:
>Folks,
>
>I've been tasked with "guaranteeing" that the backup vtapes or in the
>future real tapes are "good." So I found the command amverify that
>seems to be the correct routine but I want to know does it completely
>check the archive and the files contained within?
AIUI, only that the media is readable without errors. I don't believe that a
bit for bit compare has ever been attempted by any backup procedure.
Bear in mind, and bring it to The Powers That be attention, that a verify pass
on a real tape counts as one pass through the drive, and it also counts as
wear and tear on the drive.
A vtape verify pass is essentially free since the disk drives heads do not
touch the disk, but fly a micron or two above the surface on a film of air
carried along by the spinning disk, so there is not a major wear and tear
consideration for disk drives, particularly if they spin 24/7.
A tape drive, even the helical scan types, still have tape to head (and to the
guides and drive rollers too) contact, real physical contact, so the wear is
often calculated to be x number of running hours. Only because the tape is
stopped 95% of the time do we get operating lifetimes from a tape drive that
are even remotely comparable to the life of a modern hard drive.
Figure on 1000 to 8000 hours for a tape drive, the latter figure only
achievable in a clean room at 50F and less than 20% relative humidity. High
temps, and high humidity both make tape a lot more abrasive.
I have hard drives spinning here, right now, with over 50,000 hours on them.
And no bad sectors according to smartctl.
Your management would be served a lot better, by filling a 500GB drive and if
long term storage is needed or demanded, put that drive in the safe, offsite,
until such time as the data is too old, and then recycle it back into the
system just as if it was a 2 year old tape. The costs might be a bit more
than for equ tape storage, but at this stage of the technology, I'm convinced
the hard drive is the more dependable device of the two. I switched about 3
years ago, don't worry about offsite or long term as I'm just a home user,
and the hard drive has been so much more dependable I'm amazed. I had tape
trouble or drive trouble at least weekly, and I plumb wore out 4 of those
Seagate changers before I gave up. Now I just read the emails I get from
amanada, and stack the printout, and other than playing canary for new amanda
releases, I've forgotten about 'did my backup run ok' questions. Barring a
major power failure, which we had last night, it Just Works(TM).
YMMV of course.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The beauty of a pun is in the "Oy!" of the beholder.
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