On 07/05/2013, at 09:15 a.m., John Drescher <drescherjm AT gmail DOT com> wrote:

>> I see that LTO 6 holds 2.5T data per tape, or 6.25T compressed.
> 
> The 6.25TB is only an estimate. If you have non compressible data you
> will get close to 2.5 TB of space on your tape. If you have all text
> files you may fit 15 TB on a single tape..
> 
>> I've never used HW compression before so am wondering whether its
>> performance is variable like SW compression.   i.e. depends on the
>> file contents just what kind of compression ratio you'll get.
>> 
>> And also how reliable is it?   If it is just as reliable why would
>> someone choose not to use it (and therefore why is there an option to
>> not use it)?
> 
> HW compression is 100% reliable. Just leave compression on at the HW
> level and make sure you have software compression off. HW compression
> will not slow down your backups and it will not reduce your tape if
> you have non compressible data.
> 
> John
> 
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Currently I have a LTO3 magazine with HW compression on. From a theoretical max 
storage of 400GB, sometimes it gets very good compression rates, and manages to 
fit near 700GB. I had it turned off before, and since I turned it on I haven't 
noticed any difference in backup time. My recommendation: turn off SW 
compression and let the hardware do its job.

LDC - Gustavo El Khoury
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Learn Graph Databases - Download FREE O'Reilly Book
"Graph Databases" is the definitive new guide to graph databases and 
their applications. This 200-page book is written by three acclaimed 
leaders in the field. The early access version is available now. 
Download your free book today! http://p.sf.net/sfu/neotech_d2d_may
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