[rescue] Backups

velociraptor velociraptor at gmail.com
Thu Jun 16 12:44:09 CDT 2005

On 6/16/05, Jeffrey Nonken <jjn_rescue at nonken.net> wrote:
> On Thu, 16 Jun 2005 10:09:21 -0500 (CDT), Mike Hebel wrote:
> > Just a note on price - the DLT drives are cheap because they are
> > corporate take-outs usually.  Nine times out of ten they were taken
> > out because of capacity not wear.  I've met very few DLT drives
> > that needed anything more than a cleaning tape to ensure proper
> > operation.  DLT3000/4000 drives are cheap because one hard drive is
> > now often beyond the capacity of a single tape.
> OK, good to know. I'm still not sold on DLT but I'll take a look.

Just a point of data: All linear tape solutions (DLT, AIT, LTO) are
rates for millions of reads/writes.  Both the tape drives and the
tapes are extremely hardy.  I did a bunch of research on this
when trying to decide b/w the three 2 jobs back.

It's quite rare to even encounter media errors with these types of
tapes, IME.  Until recently here at the latest work, I had never
seen any DLT media errors, though I had previously encountered
the "hook" on the end of the tape being torn off.  I have seen the
mechanical bits of DLTs fail, but do not recall having seen head

Linear tapes have a single reel--there is a tab on the end of the
tape that is grabbed by the tape drive, then the tape is wound
at very high speed into the drive for reading/writing.

The most important consideration for maximum tape writing
efficiency and longevity with linear tapes/drives is the data
stream to the tape drive.  If there is not sufficient data being
fed to the drive, the tape will "see-saw" over the tape head
wearing both the tape and the tape head.

The tape see-saws because data is written in bands onto
the tape, e.g. a hypothetical block looks like:


Ircc, with LTO there are twelve bands.  The tape drive will fill
up all bands across a block of tape before going to the next
block.  It _can_ write all bands simultaneously, if it has the
data to feed it.  In the worse case, it would pass the same
spot 12 times forward and backwards on an LTO.

I suspect IDE will likely not be fast enough to feed the
beast unless you stream multiple jobs across the net-

> > But if DVDs will work for your amount of data then fine.  I think
> > you'll have trouble implementing that on a 'nix system though.
> > Someone mentioned  using cdrecord but I'm pretty sure that doesn't
> > span.

>From a personal standpoint, to do backups as opposed to HD-
based replication of data, I'd really have to have some sort of
tape library.  And if I am going to do that, I'd rather pony up the
bucks and get LTO (the latest DLT drives are not compatible
with the older stuff, though with the surfeit of DLT drives on the
market, a couple of spares is not that big of a deal I suppose...
but more stuff cluttering up the already cluttered space! :-/).

I suppose I could chuck the notion of backing up all the media
files that I have original media for and just go RAID 5 on those,
which would cut things down considerably. Decisions, decisions.



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