OT: redhat

Tue Nov 9 20:37:36 PST 2004

On Tue, Nov 09, 2004 at 04:47:54PM -0500, Bill Vermillion wrote:
> On or about Tue, Nov 09 12:25 , while attempting a Zarathustra 
> emulation Jay R. Ashworth thus spake: 
> 
> > On Sun, Nov 07, 2004 at 06:04:36PM -0500, Fairlight wrote:
> > > You'll never BELIEVE what Bill Vermillion said here...:
> > > > I've seen that too. Using 2GB+ is not unusual in Linux, but using 
> > > > more than 100MB in FreeBSD / is unusual.  Though the 5.x has
> 
> > > I think Bill said that one of the latest (SuSE 9.2??) uses
> > > over 6 gigs if you install everything, wasn't it?
> 
> > Might have been me.  9.1 is very close to that.
> 
> > > People really should replace their media once in a while, as
> > > well. I can't believe anyone could -miss- tapes being off the
> > > reels. But tape just goes bad after a while, as well. I dunno
> > > what the rule of thumb is, but I should guess that replacing
> > > the batch of tapes at least once a year is a prudent move.
> 
> > That's what we spec, even though that's only 50 passes, which is
> > considerably less than what the tapes ought to be good for.
> 
> I have clients use separate tapes for Mon, Tue, Wed, and Thur
> and four tapes for Friday.
> 
> These are DDS3 DATs and 2 years is not a problem.
> 
> If anyone is using QIC devices they can vary greatly.   You can
> make up to about 30 passes on a tape when recording as you reverse
> and go the other direction for each track, and then if you do
> a complete verify that also adds up.
> 
> The old AT&T systems would default to >I think> 2000 passes per
> tape.  These were smaller QICs and you would use at least 8 passes
> on each backup, and then when you hit the preset limit you would
> get a warning.  I believe the AIT also uses a warning, but I'm not
> sure.
> 
> Perhaps Tom could let us know which emit the warnings.
> 
> Bill
> -- 
> Bill Vermillion - bv @ wjv . com
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Always, tapes have been good for many thousands of passes, given
that people were doing proper head cleanings, which would be recommended
at about once per week for drives doing nightly full system backups.

Unfortunately, no one really maintains tape drives. I've had situations
in support where we've asked people who've had a tape drive for 5 or 6
years when it was last cleaned.

 "Cleaned? How do you do that?"

So conventional wisdom is to rotate tapes once every year (50 backups)
or 2 (100 backups), AND clean them religiously.

Fortunately, all modern tape drives support an industry-standard
diagnostics mechanism called TapeAlert(tm), first pioneered by
Hewlett Packard. Drives with TapeAlert support can diagnose themselves,
their environment, and their media, and queue messages for
software that is capable of asking for it.

TapeAlert can alert the user to many problems, including tapes
that have snapped, drives that need cleaning, termination or
undervolt/overvolt conditions, or even media that is having
correctible read or write errors but needs replaced, BEFORE
any data is lost. We've even had a tape drive here report that
it was about to fail, and tell us to stop using it.

A list of TapeAlert messages can be obtained from the "Whitepapers"
link of the Microlite home page. ONE reported TapeAlert message
can be a lifesaver.

BackupEDGE has been supporting TapeAlert diagnostics since 1998.
Lesser products still ignore this capability, which boggles my mind.

Funny BackupEDGE support story...

  "There must be something wrong with BackupEDGE. I can't do backups
   on Fridays?"

     "What happens on Fridays?"

  "Well, my consultant gave me a new batch of tapes, and said
   'make sure you put THIS one in every Friday', so I do, but after
   about 30 seconds it just pops back out!"

They never even looked at the label on the cartridge.
--- 
Tom
---
 D. Thomas Podnar
 tom at microlite.com         http://www.microlite.com
 Microlite Corporation     724-375-6711 Voice
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