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Looking for tape drive recommendations

Posted on 2005-03-29
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I currently have an internal DLT IV 40/80, and I'm looking to replace it with something a bit bigger, preferably at least 100/200gb. Backup speed is not as important as reliability.

I don't have anything specific in mind, I'm looking for suggestions, trying to get an idea what's out there.
What do people think about LTO vs DLT, internal vs external, etc. What brands are reliable? Any products I should avoid? What about Autoloaders?

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Question by:billmercer
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HTeunis earned 964 total points
ID: 13651313
Hi,

Recently we work more and more with the LTO drives, wich I like alot. They are fast (altough you didn't ask for it), relative cheap for what they offer and reliable.

The question internal or external, is very similar to a internal/external dat drive, dlt drive, whatever drive and you prolly can answer that question for yourself.

Autoloader and/or robotic libraries are nice, but kinda expensive if your looking for a backup solution in the 100-200 GB range.

There are several suppliers offering the LTO drives.
We often work with the HP LTO drive of Freecom.

HP LTO offers more product info, software and good service/support.
Freecom are cheaper to purchase, and we supply the OEM versions without any documentation/software and so.

Good luck
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by:Duncan Meyers
Duncan Meyers earned 884 total points
ID: 13651535
For reliabilty: LTO, LTO and LTO.

SDLT are good, but not as good as LTO drives. LTO drives are made by either IBM, HP or a spin-off from Quantum or Seagate (I think) named Certance.

The main difference to be aware of between IBM and HP drives is that HP drives can steplessly vary the tape speed to match the speed of incoming data from the server, whilst IBM drive speeds are stepped - that is, they'll run at (for example) 7inches per second, 10ips, 14ips and so on, so typically (and paradoxically) you can expect better performance with an HP drive if you have a slower backup server.  I've been told that Certance drives are like the HP drives with continuously variable tape speed although I haven't checked this for myself.

A DLT drive does things differently. It has a fixed tape speed. You write data to the drive and the drive streams out to tape. Once the  drive runs out of data to write, it stops and waits for the next command/data to write. It now has to reposition the tape to the end of the last write before it can continue to write out new data. This process is often called 'shoe-shining' because of the backwards-forwards motion of the tape over the read/write heads and it is why (again, much more obvious with an older, slower server) the DLT drive seems to pause frequently during a backup operation. It's also why an LTO is much faster than a DLT.

I like LTOs :-)

Go for an external drive so that if the drive fails you don't have to shut down the server to replace it. If you have a dedicated backup server then it doesn't matter. I'd suggest an Adaptec 29160/39160 as they are able to rescan the SCSI bus during normal operation and so will recognise a new device - although you need a minimum of W2K for this to work.,

As for libraries, I have a preference for Storagetek over ADIC and Quantum, but they really all are pretty much of a muchness. Most are rebadged Storagetek and ADICs anyway. HP used to do their own range of libraries which were pretty good. I don't know if they still make their own, though.
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by:dovidmichel
ID: 13652946
From my perspective I think both LTO2 and SDLT are winners, but I'd go for SDLT over LTO2. One nice thing about SDLT600s is they support WORM with regular tapes.

Autoloaders are great for unattended operation, if you have the money to spend. Figure out how much data there is to backup, how much data there is expected to be next year, and how many days of unattended operation you would like.
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by:Rahul Misra
ID: 13653595
SDLT600
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by:Duncan Meyers
ID: 13656995
WORM = Write Once Read Maybe

:-)
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by:billmercer
ID: 13658887
Meyersd, I'm not sure, but I'm getting the suspicion that you might be biased in favor of LTO.

How's prices for LTO versus SDLT? Don't all these variable-speed motors mean a higher price for the same storage?

I've had to replace my current drive twice under warranty (another reason I'm looking to replace it) and one time it went south and took a couple of tapes with it. In some ways I think the drive reliability is more important than the media reliability.

What about brands? Is Exabyte still considered dreadful? I noticed Tandberg is selling LTO drives also.

The main reason I'm considering an autoloader is to reduce the backup screwups. It's amazing how often we've lost good backups due to people swapping the wrong tapes, not following the schedule, etc.
"Oops, I forgot to put this tape in yesterday, so I'll just put it in this morning, and nobody will notice..."
But I have a hunch it's not going to fit in this year's budget.


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by:Duncan Meyers
ID: 13658993
>Meyersd, I'm not sure, but I'm getting the suspicion that you might be biased in favor of LTO

Really?

:-)

I work in the enterprise environment and I see more hardware than I care to admit - I've had reliabilty issues with DLTs - and also quality issues with repaired DLT drives (funnily enough Exabyte Canada rework centre has been the main offender). LTO drives still have their fair share of failures, but I've found them to be considerably more robust than DLTs. LTOs do not tend to have the sort of head alignment issues that DLTs have. Whether that is because the design is more tolerant of misalignment or that DLT reworkers do a crap job of alignment I do not know...

Pricewise the technologies are line-ball Gigabyte for Gigabyte for the drives and media. FWIW - in LTO I'd go with HP drives (for the reasons I've outlined above) and media  Fuji, TDK or Sony are all good. iMation seem OK although I've had issues with their DLT stuff in the past. I haven't seen any discernable difference in reliability between the IBM and HP drives.

Funnily enough, by far the most robust technology by far is the 9840 - an **old** mainframe technology that many would consider past its use-by date. But it is solid, solid stuff. Expensive compared to LTOs and DLTs though
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by:dovidmichel
ID: 13659008
Since Exabyte has commited to the VAX drives they are off my top list, and Tandberg just never seemed to make the transistion and got lost in the shuffle. ADIC is ok but at the lower end of the quality range based off what I have been seeing.

Overland Data still seem to put out good libraries. Quantum/ATL, IBM, StorageTek all put out top quality libraries.
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by:Duncan Meyers
ID: 13659221
>ADIC is ok but at the lower end of the quality range
I'll second that...
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by:samccarthy
ID: 13662288
I replaced all my DDS4 drives with new Sony AIT-3 Tape Drives.  The AIT-3 is very fast and reliable.  It has a 100 - 260gb capacity.  I use 12 tapes in rotation, 1 per week, so I have 12 weeks of backups.  The drive has a 3 year warranty and sony support has been great if you ever need it on their drives.

The drive will set you back say $1700 and if you add an Adaptec controller and 15 tapes, you are looking at about $2500 total.
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by:billmercer
ID: 13672043
I hadn't considered AIT. Is AIT-3 the same thing as SAIT? Anyone care to elucidate the relative merits of AIT versus LTO?


Yikes, those 9840 drives ARE a bit pricey, aren't they? Guess that's not an option.
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by:dovidmichel
ID: 13672618
The AIT drives are good, fast, high capacity, but not as reliable as either LTO or DLT.  
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by:samccarthy
ID: 13680130
The SAIT are the next generation so to say of the AIT line with a higher capacity.  When I jumped to AIT-3 from DDS, I got a big jump in performance and much greater capacity all off the same controller.

I have been very impressed with their reliability.  At the city I work for my only problematic drive has been a DLT and Media problems have always been DDS4.
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by:billmercer
ID: 13685838
I think I've settled on LTO, mostly because of negative experiences with DLT drives. The AIT drives I've looked at don't seem to offer anything more than the LTO.

On a separate note, these AIT product descriptions all seem to claim 2.6-to-1 compression. That strikes me as extremely deceptive. It's bad enough that everyone brags about speeds and capacities that are only applicable if you get  2-to-1 compression, which I never come close to. But now I'm supposed to believe that a different tape format will give me 30% better compression? Native storage is what I go by, any extra I get due to compression is gravy.

I'm considering this guy...
http://www.certance.com/products/lto-ultrium/lto2/CL1002-SS
The price seems remarkably low compared to other 200/400 drives.


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by:Duncan Meyers
ID: 13685916
>On a separate note, these AIT product descriptions all seem to claim 2.6-to-1 compression

It's optimistic to say the least. Real world conditions you may see 1.5:1. I have seen up to 4:1, but that was a huge SAP databse that was full of empty tables, so I guess it doesn't really count...

Certance was first to the market with the new drives which has pushed down the price of the older LTO-2 drives and media.
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by:samccarthy
ID: 13686504
AIT Drives do get much better compression than say 2 to 1 DDS.  I can tell you from experience with these drives that I regularly get 170 to 200 gb during my week of backups on a single tape and have yet to run out of room.
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by:billmercer
ID: 13686797
But sammccarthy, how can the tape medium affect the compression? The compression has to output a stream of bits, and the same bit stream could be written to any medium. The type of data determines what ratio you're going to get. Sparse database files compress far more than executables, which compress more than JPEG images or MP3 files.

I'm not saying you don't get that ratio on your tapes. I'm saying if you do get that ratio with AIT, you should get pretty much the same ratio with any tape drive that uses compression based on Lempel-Ziv, which is most of them. The algorithm used to compress data for AIT is ALDC, which was developed by IBM. In their white paper on the subject, they brag about their enhancements to the LZ algorithm increasing compression ratios from 1.6 to about 1.7, and they consider this a significant improvement. No 2-to-1 is ever claimed, and certainly no 2.6-to-1. They also mention LTO as another platform that uses their compression. How can Sony turn around and claim a ratio that is so much bigger than what the developers themselves claim? It's deceptive.

http://www.research.ibm.com/journal/rd/426/slattery.html 

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by:billmercer
ID: 13686813
Thanks to everyone for your suggestions and comments. A very interesting discussion.
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by:samccarthy
ID: 13690913
Compression is done at the hardware level or software level.  Media is Media.  My DDS4, using hardware compression built into the drive regularly got say 27gb on a tape with a maximum compressed capacity of 40gb.  When I was researching drives, one of the things that impressed me was the higher compression ratio with the AIT drives.  The DDS4 got a 2 to 1 ratio, however the AIT got a 2.6 to one.  One article I read explained that the AIT was much more efficient at the compression.

I have experienced this myself.  Using the same ratio's as the DDS4, I would have run out of space numerous times, but I have not.  I regularly get more compression out of the AIT and at a much faster speed than my former drives.

According to Sony and the industry, Adaptive Lossless Data Compression technology (ALDC), previously available only in mainframe-type tape drives, provides substantially greater compression (2.6:1) when compared to older, IRDC or DLZ compression algorithims.

Here is what Sony claims, • Adaptive Lossless Data Compression (ALDC) provides greater data compression efficiency ¡V offers average compression of 2.6:1.

Here is a data sheet about AIT http://www.interfaxsystems.com/products/pdf/AIT_3Datasheet.pdf#search='AIT3%20Data%20Compression'

Finally, here is what IBM says. www.research.ibm.com/journal/rd/426/craft.html  This is research they did in 1998 as they were developing this.

ALDC compression ratios depend on the data, but are such that capacity for a typical computer DASD storage system can be increased by a factor of 2 to 3 by deployment of this algorithm. Many commercial computer customers often purchase systems for which the DASD cost is the dominant factor, ranging from tens of thousands to millions of dollars per system, so clearly this kind of increase in DASD storage capacity, for less cost than one additional chip, is a significant advance.

More recent work on using small hardware preprocessors to improve the compression of ALDC for other data types has shown promising results. The BLDC algorithm, which combines ALDC with specialized preprocessor hardware for high-resolution binary bitmapped image data, is described. Results are given for one typical application, in this case a set of laser printer page image data files. Compression improvement over ALDC ranges from 1.5 to more than three times better.

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by:samccarthy
ID: 13690914
Bummer, not even a share for offering a good alternative.
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