Not worthwhile to buy LTO-6 tapes for differential backups

[Ted4356]

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?

[Jaydeep_S]

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]

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 http://www.symantec.com/docs/HOWTO22778. 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. 

[Ted4356]

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.

[Donald_Eady]

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

[pkh]

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.

[Jaydeep_S]

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.

[ZeRoC00L]

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.

[Biker_Dude]

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:

http://h18000.www1.hp.com/products/quickspecs/13572_na/13572_na.PDF