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what sort of capacity can tape backup handle?

Posted on 2004-10-02
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Last Modified: 2010-04-03
I'm setting up a cluster thats going to have two nodes each sharing two external DAS HDD enclosures with combined storage of 6 TB.  I'm wondering - can tape handle that sort of volume of data?

if i want to do a tape backup each night - can I?  If tape can handle that much data - do all tape setups handle that much data?  How long does it take to dump that much data to tape?  

Do i have to take my system down to dump to tape?
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Question by:kenshaw
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Lee W, MVP earned 500 total points
ID: 12210697
You would need a tape library - either SDLT or LTO, would be my recommendation.  Each one holds a minimum of 100GB per tape (uncompressed).  Newer SDLT technologies handle 600 GB compressed - meaning that, assuming your data compresses at a 2:1 rate, it would probably take 10 tapes to do a full backup - at $100 per tape... (guessing), that's $1000 per full backup.

Throughput is advertised at 72 MB/sec compressed.  Means that a FULL backup would take ~1 day, at full speed.  NOTE: you RARELY see these numbers in real life.  Better to double them and that's going to be closer to what you actually experience.

Now, what I recommend you do is:
Setup a backup schedule where you backup 1/4 - 1/8 of the drive each weekend day (assumes your usage is noteably lighter on the weekends).  This would give you a full every 2-4 weeks.  Then, during the week, do a differential backup every other day of the week.  In addition, you'd probably need to get a library with AT LEAST 2 tape heads.  Why?  What happens if the drive goes bad and you have to do a restore?  Having a second head also means you could run two backup jobs simultaneously.  Tape libraries of this nature will typically run you $16000 on the low end and high 5 figures on the high end.
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by:Cyber-Dude
ID: 12211280
leew suggests a good offer here but, I would consider an external storage provider to create an DRP site. This is due to the reason you are using a large data capacity and I think that this is an important issue at your company (i.e. keep data structure).

Links:
About Disaster Recovery Plan:
http://www.comp-soln.com/DRP2_whitepaper.pdf

Cyber
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Expert Comment

by:Duncan Meyers
ID: 12213988
Soon to be relased LTO3 tapes are 400GB native, 800GB compressed. Worth waiting.
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by:Lee W, MVP
ID: 12214058
Not worth waiting if you have a problem next week and no backup because you were waiting.  In addition, SDLT drives can generally read older DLT and SDLT tapes.  BUT if you don't have any of those, this is irrelevent.

Wait if you absolutely can wait.  But otherwise...  It's also worth comparing media costs and numbers needed.  And I STRONGLY recommend against going with the hype - in other words, IGNORE references to compressed capacities.  If you're backing up MPEG files and ZIP files, you're compression is going to awful.  If you're compressing database files, then you might see EVEN BETTER than 2:1 compression.  Go with RAW uncompressed formats in your analysis - or at least be VERY conservative in your expected compression - 1.1:1 or 1.25:1 if the files backed up are a wide variety.
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by:Duncan Meyers
ID: 12214063
OK.

Worth waiting for if you can.

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