On 7/25/2011 6:14 PM, James Harper wrote:
>> 2011/7/25 Rickifer Barros<rickiferbarros AT gmail DOT com>:
>>> Hello Guys...
>>>
>>> This weekend I did a backup with a size of 41.92 GB that took 1 hour
> and 24
>>> minutes with a rate of 8.27 MB/s.
>>>
>>> My Bacula Server is installed in a IBM server connected in a Tape
> Drive LTO4
>>> (120 MB/s) via SAS connection (3 Gb/s).
>>>
>>> I'm using Encryption and Compression Gzip6.
>> Disable software compression. The tape drive will compress much faster
>> than the client.
>>
> If you can find compressible patterns in the encrypted data stream then
> you are not properly encrypting it. The only option would be to compress
> before encryption which means you can't use the compression function in
> the tape drive unless the tape drive also does the encryption (some do).
>
> Use a lower GZIP compression level to see if it gets you better speed
> without sacrificing too much performance... I suspect the speed hit is
> going to be the encryption though.
>
> James
>
I was under the impression that _all_ LTO4 drives implemented encryption 
(though if having the data traversing the LAN encrypted is your goal, 
you'd still have to do something).  I don't know enough about it to know 
how good the encryption in LTO4 is, however (or for that matter, how the 
key is specified).

Both encryption and compression in SW are going to be much slower than 
the tape drive could do it (which is why LTO4 required it, as I 
understood).  Another point, even with your current config, if you 
aren't doing data spooling you are probably slowing things down further, 
as well as wearing out both the tapes and heads on the drive with lots 
of shoeshining.

-se

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