Zitat von Conrad Lawes <[email protected]>:
I have been using Bareos for a couple years now and Bacula (Community Edition) a few years before that.One thing that I have never gotten to work is hardware compression. I used to use LTO3 tapes that natively storage 400GB and 800GB with compression. Never got beyond 400GB.I've upgraded by tape library to a Dell TL2000 tape library with LTO6 tape drive. LTO6 natively stores 2.5TB and 6.25TB with compression. Hardware compression is turned on. However, I never get above 2.5TB of data on each tape.I read somewhere that you must spool your data before writing to tape because Bacula/Bareos requires a steady stream for compression to work. Tried that, still no dice. And yes, I have disabled soft compression for my backup jobs. All the documentation I found online are limited and/or out-of-date.I'm presently using 2 LTO6 tapes to complete a full backup (~3.5TB of data). Obviously, my 2nd tape is under utilized and should not be required if 6.25TB capacity is achievable.Is there any H/W compression expert that can shed some light on what is required by Bareos to get compression working as advertised?Thanks.
To my knowledge the LTO device automatically try compression on the delivered data. If the compression ratio is too small or negative the compression is turned off. What is needed to get a good ration is always the same:
- data which are not already compressed, so no jpeg,mpeg,zip and the like - no compression done in software before transfering the data to tape- no encryption because this hides the redundancy the compression is looking for
spooling data is about speed, not compression. So simply do fill a tape with well compressable data and compare the ratio with for example a zip archive.
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