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DLT vs DDS

Posted on 2004-10-12
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Last Modified: 2008-01-09
Hello all,

I was looking at getting a dell powerVault 112T.  When going through the purchasing options I noticed that the DLTVS80 drive for it was significantly more expensive than the DDS4 drive.  Would anyone happen to know what advantages DLT has over DDS?  

Thanks in advance.
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Question by:joshuaemory
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by:Lee W, MVP
ID: 12288695
DON'T BUY DELL TAPE DRIVES!

With my past job and a client they purchased SEVERAL dell tape drives and I think the failure rate was 75% - we replaced drives and whole units several times in the first few months of ownership.

I'll admit - this info is a year or so old, but we switched to Overland systems and they worked flawlessly (though I understand recently they've had problems with a couple units, but by this point the units are at least 2 years old.  
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Lee W, MVP earned 250 total points
ID: 12288717
That said, DDS tapes hold 20 GB uncompressed, DLT tapes hold 40GB uncompressed.  SDLT does 160 or 300 GB, depending on the drive model.

DLT also has faster potential throughput.  SDLT faster still

DLT/SDLT is a larger tape, roughly 1x3x3 inches, where as a DDS is only a little larger than a microcassette tape.

If you're backing up large or relatively large drives, go with DLT or preferrably SDLT as I doubt your data stores are going to get SMALLER.
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by:masterbaker
masterbaker earned 250 total points
ID: 12289071
Check out this link:

http://www.dell.com/downloads/global/products/pvaul/en/pv112t_spec.pdf

That has the specs on the three drive options (DDS4, DLTVS80, and DLTVS160).  

Basically you need to think about how much data you need to backup for your largest job (such as a nightly full backup of your data) and how quickly you need it done.

Do you need to only backup a few gigabytes over an entire evening?  Any drive will do for that.

Do you need to backup 80GB in a 4 hour window?  If so, the only option is the DLTVS160.

If you look at the 2nd page of that link, you'll see the drive speeds and storage.  DDS4 and DLTVS80 will backup around 11GB per hour.  DLTVS160 is about 33GB per hour.  

You just need to think about the size of your backup jobs, whether or not you want to swap tapes in the middle of a job, and the size of your backup time window.

By the way, I have had good experience with Dell tape drives.  I'm not sure if they are all re-branded ADIC drives, but I know at least a couple of models are.  ADIC makes great backup systems, so as long as Dell doesn't mess with them, they'll be good as well.  You'll always find people with good and bad experiences with every brand.  No one is perfect. :)

Jeff
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by:Lee W, MVP
ID: 12289178
Jeff,

I agree with the no one is perfect.  My experience is with:
TWO PowerVault T130 (DLT)
ONE PowerVault T136 (SDLT)
TWO PowerVault T120 (DDS)
ONE PowerVault T120 (DLT1)

The only unit that never gave me problems was the T120 DLT1.  The two 130's were consecutive systems; one replaced the other after NUMEROUS drive failures.  Then the other had a few failures before it finally settled down.
The 136 worked great for 6 weeks, then we couldn't use it for a month
The 120 DDS worked for a while then got jamed and we had to send it back to Dell - they never returned the tapes - WITH backup data.

MAYBE they improved over the past year, but I've used ATL, HP, and OVERLAND systems, and never had such consistant problems.
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by:andyalder
ID: 12289931
DDS sounds cheaper than DLT and the media is less but when you look at the cost over time you find that DDS heads wear out quicker than DLT and the media wears out much qicker, probably 4 times as fast.  With DDS there are guide pins and rollers that touch the recording surface wearing it out, the only thing that touches the recording surface of DLT is the head.
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Author Comment

by:joshuaemory
ID: 12290588
Thanks a lot for the advice everyone.  You've all been very helpful.  Against my nature I've decided to not be stingy and go for the DLT drive...
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by:masterbaker
ID: 12290983
Good choice!

If you do want to save a few bucks, you can often pick up new DLT tapes on eBay for a fraction of the cost!  I have purchased several lots of 5 tapes on there for less than 1/3 the new price.  

Just steer clear of used tapes.  You never know what you're going to get, and backups are important!

Jeff
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