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I am using BackupExec and it is asking for second tape. I am using LTO-3 ultrium 800 gig 2:1 compression tapes and it stops and asks for secound tape at 558,916,035,547 Byte count. Is my setup wrong or do i just need to get larger tapes?

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up vote 6 down vote accepted

LTO 3 has 800 GB capacity at the assumed compression ratio of 2:1, which is very optimistic in most cases. The physical capacity is 400GB, and in my experience a compression ration between 1.1:1 to 1.5:1 is much more realistic, but that is very much dependent on your data.

If you have an LTO4 drive, you could also use LTO4 tapes which have double the capacity. LTO-5 is the current generation with 1.5TB native capacity, but these drives can only read LTO3 tapes, not write them.

For more info, see Wikipedia.

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thank you for the response that is what i thought ordered bigger tapes . :) – volcer Feb 28 '12 at 17:20
+1. Actually you may have a backup software already compressing which then means the tape has little left to compress ;) – TomTom Feb 28 '12 at 17:20
@volcer: Using LTO4 tapes is only working if you have an LTO4 drive, so be sure to check your drive type. – Sven Feb 28 '12 at 17:22

What that means is that you get 800GB when the compression is 2:1. You must be getting less than 2:1 compression so that's why you're only getting 550GB or so on your tape. Nothing is wrong with your setup.

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thank you so much for the response i thought that was the reason – volcer Feb 28 '12 at 17:01

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