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Date:      Mon, 27 Oct 2003 21:26:20 -0500 (EST)
From:      Robert Watson <rwatson@FreeBSD.org>
To:        Stefan Walter <sw@gegenunendlich.de>
Cc:        current@FreeBSD.org
Subject:   Re: GBDE performance on ZIP disks
Message-ID:  <Pine.NEB.3.96L.1031027212114.99244E-100000@fledge.watson.org>
In-Reply-To: <20031027125318.GB1582@kyuzo.dunkelkammer.void>

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On Mon, 27 Oct 2003, Stefan Walter wrote:

> is there a way to speed up writing to a gbde encrypted ZIP disk? 
> Copying 37 MB of data to an encrypted disk (in a SCSI drive) that has
> been initialized with "newfs -O 2 -U /dev/da1a.bde" takes ~180 seconds,
> which is ~200KB/s. Copying the same amount of data to the disk without
> using gbde takes ~50 seconds, which is ~740KB/s. 
> 
> I guess this problem is similar to the one you have when using msdosfs
> on a SCSI ZIP drive, which is also very slow. 
> 
> Using a different sector size than the default 512, which is also the
> sector size of the media, doesn't seem to be possible and always results
> in a "gbde: write sector 0: Operation not permitted". Playing around
> with newfs's options didn't help so far, either.

How do things look performance-wise if you do a raw sector read comparison
with dd at various blocksizes?  My recollection is that our msdos code
would benefit hugely from the addition of clustering support, but UFS2
with a fragment size matching GBDE's notion shouldn't present the same
problem...

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Network Associates Laboratories




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