reliability of Ultrium2/LTO- vs a DDS/5 - tapedrive

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hardware55

Hello

I`am contemplaing about buying an LTO2- or a DDS5-tapedrive.

Which drive is more reliable?

(I do know that`s not fair to compare those drives because
of speed and capacity (and price), but at the moment I am
only interested in reliability)


Any tip is appreciated very much. Thank you!

John
 
You're basically comparing an 18-wheeler to a pickup truck. DDS is the
lowest grade of tape that anyone in his right mind would consider for
anything of real importance, but it is not "good", it is just sufficiently
"not bad" to be usable. LTO and DLT are good-DLT has a long track record
and one of the design objectives for LTO was out out-DLT DLT.
Click to expand...

John,

Just guessing that the OP may have been a troll.

Back on topic: How does Exabyte's VXA fit into this arrangement?

They claim incredible reliability for the media AND they claim that
they are the only technology where the tape speed will slow down if
the drive isn't getting data fast enough. (I.e. no "shoeshining.")

-
 
Hello

I`am contemplaing about buying an LTO2- or a DDS5-tapedrive.

Which drive is more reliable?

(I do know that`s not fair to compare those drives because
of speed and capacity (and price), but at the moment I am
only interested in reliability)


Any tip is appreciated very much. Thank you!
Click to expand...

You're basically comparing an 18-wheeler to a pickup truck. DDS is the
lowest grade of tape that anyone in his right mind would consider for
anything of real importance, but it is not "good", it is just sufficiently
"not bad" to be usable. LTO and DLT are good-DLT has a long track record
and one of the design objectives for LTO was out out-DLT DLT.
 
Lady said:
John,

Just guessing that the OP may have been a troll.

Back on topic: How does Exabyte's VXA fit into this arrangement?

They claim incredible reliability for the media AND they claim that
they are the only technology where the tape speed will slow down if
the drive isn't getting data fast enough. (I.e. no "shoeshining.")
Click to expand...

Exabyte has a long track record with 8mm helical scan. I've not used a VXA
myself but would expect that they would be quite good from a performance
and reliability viewpoint. Like all helical-scan I'd expect them to need
regular (as in religiously attended to) cleaning for best reliability.

Downsides I see are media cost and their being single-source--you can get
LTO-1 drives in the same price range and the 100 gig tapes are cheaper than
the 80 gig VXA tapes, and if Exabyte goes under or decides for whatever
reason to drop the product line you're screwed, while with LTO there are
several manufacturers.
 
Exabyte has a long track record with 8mm helical scan. I've not used a VXA
myself but would expect that they would be quite good from a performance
and reliability viewpoint. Like all helical-scan I'd expect them to need
regular (as in religiously attended to) cleaning for best reliability.

Downsides I see are media cost and their being single-source--you can get
LTO-1 drives in the same price range and the 100 gig tapes are cheaper than
the 80 gig VXA tapes, and if Exabyte goes under or decides for whatever
reason to drop the product line you're screwed, while with LTO there are
several manufacturers.
Click to expand...

J Clarke,

You have very good points about Exabyte being a single-source and the
relative costs of VXA and LTO, for media costs in particular. I like
the higher media capacities of the newer generations of each kind of
drive, but I am concerned about the 12 MB/sec data transfer rate, in
my home LAN network.

How do corporations achieve that kind of data rate? What network
hardware? What backup software?

-- thatcher --
 
You have very good points about Exabyte being a single-source and the
relative costs of VXA and LTO, for media costs in particular. I like
the higher media capacities of the newer generations of each kind of
drive, but I am concerned about the 12 MB/sec data transfer rate, in
my home LAN network.

How do corporations achieve that kind of data rate? What network
hardware? What backup software?
Click to expand...

Why only 12MBps, 540MBps is on the horizon:
http://www.lto.org/newsite/html/roadmap2.htm
or 160MBps for now:
http://www.certance.com/products/lto-ultrium/lto3/CL1101-SS

Through hosts attached to the SAN?
 
Lady said:
J Clarke,

You have very good points about Exabyte being a single-source and the
relative costs of VXA and LTO, for media costs in particular. I like
the higher media capacities of the newer generations of each kind of
drive, but I am concerned about the 12 MB/sec data transfer rate, in
my home LAN network.

How do corporations achieve that kind of data rate? What network
hardware? What backup software?
Click to expand...

Generally the tape drive is in the machine being backed up unless it's a
very large system with dedicated backup servers that then have fibre
channel or gigabit links to the storage being backed up.

Gigabit is cheap now by the way--I noticed CompUSA had 5 port switches for
35 bucks a couple of weeks ago.
 
Generally the tape drive is in the machine being backed up unless it's a
very large system with dedicated backup servers that then have fibre
channel or gigabit links to the storage being backed up.
Click to expand...

Well, that machine being backed up must be one honking fast system.
Not all the systems in my lowly home LAN are in that category. (I
wish even half my systems were in that category.)
Gigabit is cheap now by the way--I noticed CompUSA had 5 port switches for
35 bucks a couple of weeks ago.
Click to expand...

Agreed. I just replaced my 100 mbit hub with a GigE switch and saw a
noticeable improvement in backup from some of the client systems. But
still not 12 MB/sec (which my current drive can't achieve, of course.)

So, go back to my comment about why I am attracted to VXA, in the
first paragraph of this posting. Exabyte claims that only VXA will
adjust tape speed to incoming data rate. Is that claim true in
practice? That is the issue for me.

--Maggie--
 
You have very good points about Exabyte being a single-source and the
Uh, I don't (yet) have a SAN on my home network. Maybe some day, but
not now. Let's get back to reality.
Click to expand...

Sorry, I forgot about a very small corporations .. ;-)
 
Lady said:
Well, that machine being backed up must be one honking fast system.
Not all the systems in my lowly home LAN are in that category. (I
wish even half my systems were in that category.)
Click to expand...

Doesn't really have to be all that fast--the main server on my home network
is a dual PIII/1000 with a single IDE drive and a RAID-5 SATA array running
Server 2K3. Copying from the RAID to the single drive I get better than 16
MB/sec--going the other way is slower due to write overhead on RAID-5--I
need a better RAID controller and will probably put one in some day.
Agreed. I just replaced my 100 mbit hub with a GigE switch and saw a
noticeable improvement in backup from some of the client systems. But
still not 12 MB/sec (which my current drive can't achieve, of course.)

So, go back to my comment about why I am attracted to VXA, in the
first paragraph of this posting. Exabyte claims that only VXA will
adjust tape speed to incoming data rate. Is that claim true in
practice? That is the issue for me.
Click to expand...

It's probably true but it's not really an issue. _Nobody_ knows how long
linear tapes last--they tried to wear out DLT tapes and gave up at half a
million passes, at which time they weren't even completely broken in--the
bit error rate was still _improving_.
 
Previously J. Clarke said:
Lady Margaret Thatcher wrote: [...]

_Nobody_ knows how long
linear tapes last--they tried to wear out DLT tapes and gave up at half a
million passes, at which time they weren't even completely broken in--the
bit error rate was still _improving_.
Click to expand...

Nice. This means magnetic tape still has a future. Any numbers on data
retention (which can be measured by determinign singal strength
degradation and factoring in ECC)?

Arno
 
J. Clarke said:
It's probably true but it's not really an issue. _Nobody_ knows how
long linear tapes last--they tried to wear out DLT tapes and gave up
at half a million passes, at which time they weren't even completely
broken in--the bit error rate was still _improving_.
Click to expand...

Nice to hear, but was that just continuous use?
Did they change tapes frequently, or simulate real world usage in
other ways?
There is more dust and mishandling in the real world than the lab...
 
Arno said:
Previously J. Clarke said:
Lady Margaret Thatcher wrote: [...]

_Nobody_ knows how long
linear tapes last--they tried to wear out DLT tapes and gave up at half a
million passes, at which time they weren't even completely broken in--the
bit error rate was still _improving_.
Click to expand...

Nice. This means magnetic tape still has a future. Any numbers on data
retention (which can be measured by determinign singal strength
degradation and factoring in ECC)?
Click to expand...

I haven't seen anything by independents but according to the tape and drive
manufacturers DLT has an archival life of 15-30 years depending on which
specific variant of DLT you're talking about.

This is borne out in practice--DLT has been in use in the video and film
production industry for a long time with so far no significant
losses--nearly all DVDs are mastered on DLT. Some of the larger houses
such as Industrial Light and Magic also use DST, which is a proprietary (to
Ampex) 19mm helical scan technology achieving 660GB uncompressed per rather
large cartridge in 1997. In that industry by the way the storage
requirements are quite large--the Lord of the Rings trilogy for example
ended up with several hundred terabytes of data, stored IIRC on LTO.
 
Mike said:
Nice to hear, but was that just continuous use?
Did they change tapes frequently, or simulate real world usage in
other ways?
There is more dust and mishandling in the real world than the lab...
Click to expand...

Been a long time since I read the report--I don't remember the details, but
mishandling is a different issue from wear due to multiple passes.

In any case now they're saying a million passes.

Not that a DLT is likely to get much dust in it--both the drive and the
cartridge have shutters. As for mishandling, you can throw a DLT cartridge
on the floor and jump up and down on it in combat boots and it still works
fine. Never tried driving a Jeep over one but suspect they'd survive that
unscathed as well.
 
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