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Tape Drive Type Recomendation

alpha-lemming used Ask the Experts™

I need to acquire a reasonably-priced SATA tape drive to do nightly backups of up to 60 GB on a FreeBSD box. I'm a little confused by all the different types of tapes and drives. What's a reliable and cheap technology for this?

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Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

The cheapest technology is disk - unless you have to archive these backups for years.  Any reason you want tape?


Company policy requires the backup media to be stored in a safe, and yes, archival lifetime is an issue.
I've looked at RDX solutions, but they don't seem to necessarily be cheaper than tape.

HP RDX solution is one of the best I've used and because it is disk based then it does tend to be more reliable, at the moment in the UK HP RDX drives are coming in a bunble for the 160gb version, where you get 3 pieces of media and the RDX drive. However don't know if this is the case in the US. This would give you all the benefits of disk as well as the added benefit of being able to store the media in a safe. Also the 160gb Media is coming down in price due to the increased capacity on newer media.
As far as tape goes there are two options - DDS or LTO.

The difference between the two is based on the quality of the system.  DDS is generally cheaper than LTO, but in the long term is more expensive due to the limited lifetime of the tapes used.  I have also found them less reliable than LTO.

DDS operates on a similar basis to tape cassettes where there are two reel built into the tape and it passes from one reel to the other.  With LTO tapes there is only one reel in the cartridge, the other reel being in the tape drive itself.  At the start of operation the tape is spooled from the cartridge spool into the machine spool.  When backups take place the tape is spooled back into the cartridge, being written to as it passes over the tape heads.  As a result, the data on the tape gets maximum protection from errant magnetic fields as the data is writtent to the deepest part of the tape on the spool.

LTO tapes have an expected life of 100 hours of reading / writing, whilst with DDS it is 20.  Both exceed this, but are a guideline.

LTO2 tape drives and tapes are very reasonably priced nowadays and have a 200gb / 400gb (uncompressed / compressed) capacity.  I would recommend LTO over DDS for reliability.



What about DLT?

Here is an interesting article about the differences between SDLT and LTO.


Interestingly, despite the claims that SDLT is more widespread than LTO, I have found that LTO tends to displace DLT when new drives are purchased.

Ah, the power of market forces.

DLT had been the market leader in enterprise tape.  But then LTO came along, and had several advantages --
1) Made by a group of companies to a standard with interoperability guaranteed, instead of single-sourced by Quantum
2) Better reliability than DLT
3) Better roadmap for performance and capacity.

Net result: Now LTO greatly outsells DLT/SDLT, and Quantum bought in to the LTO consortium.

I agree with Snibborg's recommendation of LTO.   For cheap, LTO-2 or LTO-3 will meet your needs.  If you need encryption, LTO-4 may be attractive, since it does hardware encryption with no loss of compression or performance.     Just be sure to match the tape drive performance to the feed speed your disks can provide...HP's LTO-4 is 120MB/second native, and can slow down to as little as 40MB/s.  Other drives don't scale the write speed down as well, so you have to feed them more data to keep them from having buffer under-run problems.  The native and minimum speeds for LTO-2 are 30/10, and LTO-3 are 80/28, for comparison.

Tape has a rated data retention lifetime of 30 years -- although best practice will have you going back in five years, maybe ten at most, to verify the tapes are good and that you have all the bits you need to do a successful restore (operating system, applications, license keys, service packs, info on user accounts, passwords, etc.) -- and since you're doing test restores, it may be a good time to put that data on today's tape drives, and get a 4:1 or greater reduction in the number of tapes you have to store and manage (in five years, tape will have produced two or more new generations, and capacity per tape will probably have increased 4x or so).

Oh -- Snibborg's link is pretty out of date.. it misses the last two generations of SDLT, and the last two generations of LTO!