On Sun, Sep 17, 2006 at 07:36:46PM -0500, Michael Brennen wrote:
>
> I enabled encryption on 1.39.23 using the FD keys on Friday.
> During a full backup over the weekend I noticed that the 35/70 DLT
> tapes seemed to hold less than I have seen before, about 35G in one
> case and somewhat over 30G in another.
>
> I am wondering if the encrypted data might conflict with automatic
> tape hardware compression. Would it be better to turn off tape
> compression with encrypted data?
Given that well encrypted data should be statistically equivalent to completely
random data, therefore with none of the redundancy that compression typically
takes advantage of, it's unlikely that any post-encryption compression would
produce signifigant results.
If fd side compression is applied before encryption, that would produce good
results (at the cost of even more FD cpu cycles), but tape compression probably
won't buy you much of anything in either case.
--
Frank Sweetser fs at wpi.edu | For every problem, there is a solution that
WPI Network Engineer | is simple, elegant, and wrong. - HL Mencken
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