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Not worthwhile to buy LTO-6 tapes for differential backups

Created: 12 Aug 2013 | 8 comments

We have a tape drive that is configured to use LTO-6 tapes, which we need to use for our substantial weekly back-ups.

We also run daily differential back-ups that would easily fit on one LTO-4 tape each.  We have a bunch of these lying around that we would love to use as opposed to sinking money ($100/ea) into LTO-6 tapes when we're not using them to anywhere near their full capacity.

But apparently, LTO-4 tapes are only read-only when put in a drive configured for LTO-6!

We are hoping for an alternative to just buying new LTO-6 tapes.  Has anyone else run into this issue and come up with a good solution?

Operating Systems:

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Jaydeep S's picture

Any hardware is generally 1 level backward compatible for write operations and 2 levels for read. This is what might be happening in your situation. The LTO6 Tape drive can read data from LTO 4 tapes but cant write to it.

The alternative would be to add a LTO 4 or 5 drive to be able to use those LTO 4 tapes or use LTO 6 tapes or perform backups to a disk.

Donald Eady's picture

Jaydeeps solution above should work for you. Please note that you would need to be sure that if your using a library you partition it so that the LTO 4 drive only pulls LTO 4 tapes and the 6 only pulls the 6. Additionally if you are using a library the addition of the second drive would require your purchasing a LEO license If you decide to introduce just a stand alone drive you would not need to purchase the LEO license but would still need to be sure and target the Differential jobs to the correct tape drive. 


I hope this posting was helpful


Ted4356's picture

Thanks for the information guys, what we are going to do is buy some LTO-5 tapes since the price point is a lot lower than LTO-6 and they will work for our space needs and for read/write with our current drive.

pkh's picture

I don't know if this is true when LTO6 tape drives are writing to LTO5 tapes, but when I use LTO3 tapes in my LTO4 tape drives, the write speed is significantly slower than when I use LTO4 tapes.  If this is true that the slowdown may offset your cost savings.

If your differentials are not filling up your LTO6 tapes, you can try appending a couple of differentials onto one tape.

ZeRoC00L's picture

About write-speed, that is conform specs. LTO3 can write 80MB/s LTO4 can write 120MB/s. That not only applies to the drive, but also to the tape.

If this response answers your concern, please mark it as a "solution"

Jaydeep S's picture

I agree to pkh on the performance point. About LTO6 writing to LTO5, it should work, but still better to confirm with you Tape Drive vendor once.

Donald Eady's picture

Sounds like a plan... Please dont hesitate to ask if you have any other questions in the future .. 

I hope this posting was helpful


Biker_Dude's picture

According to HP. these are the native data transfer for the 6650 (full height) tape drive:

160MB/s with LTO 6 media
140 MB/s with LTO 5 media
120 MB/s with LTO 4 media

More information may be found in this document: