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Making best use of LTO5 tape

bitmadmax
Level 2

Hi All,

I need to archive off about 30TB of data from a storage subsystem to LTO5 tape(s). The data is in the form of uncompressed files on a Windows server (documents, images, etc). 

I don't need to archive it all off, but I do want to archive most of it which allows me to make best use of a bunch of LTO5's, Ie, using the full capacity of 5 LTO tapes rather than 5 LTO tapes and a then a little bit more on a 6th tape.

Is there a way I can determine how much of this uncompressed data will fit onto an LTO5 after compression etc as I really don't want to be wasting tapes....

Thanks :)

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CraigV
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Compression is subjective and you will never get 2:1. If anything, work on a real-world compression ratio of 1.1:1 --> 1.4:1, and I personally would work on something inbetween.

Thanks!

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CraigV
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Compression is subjective and you will never get 2:1. If anything, work on a real-world compression ratio of 1.1:1 --> 1.4:1, and I personally would work on something inbetween.

Thanks!

pkh
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Images are compressed files. If you turn on compression you are likely to end up with more data than you started with., so turn off compression if you want to maximise your tape capacity.

teiva-boy
Level 6

Craig is spot on here.  Size for about 1.1:1-1.4:1, which is a more common compression rate.  

pkh
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These ratios are only applicable for uncompressed data.

CraigV
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...I suspect the data here is a mix of images and documents etc, so compression is going to be subjective. Some files MAY decompress, the rest should, but the ratio can't be accurately estimated.

bitmadmax
Level 2

So if I have an LTO5 tape which is 1.5TB native, 3TB compressed, that assumes 2:1 ratio right?

But what you are saying is you will never reach that ratio, so let's say a realistic ratio would be 1.2:1.

My uncompressed data is 3.48TB, divide this by the compressed tape size (3TB), this gives me 1.16:1, does this sound right? If so then this *should* fit onto an LTO5 right?

Thanks for all your helps so far :)

pkh
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No. You need to divide by the native capacity of 1.5Tb. Your data is unlikely to fit on one tape