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Date:      Fri, 9 Jun 2006 12:15:33 +0930
From:      "Daniel O'Connor" <doconnor@gsoft.com.au>
To:        freebsd-current@freebsd.org
Cc:        Pawel Jakub Dawidek <pjd@freebsd.org>
Subject:   Re: Data authentication for geli(8) committed to HEAD.
Message-ID:  <200606091215.41787.doconnor@gsoft.com.au>
In-Reply-To: <20060608174113.GC1075@roadrunner.q.local>
References:  <20060608132048.GD86198@garage.freebsd.pl> <20060608174113.GC1075@roadrunner.q.local>

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On Friday 09 June 2006 03:11, Ulrich Spoerlein wrote:
> I have an external HDD that I initially attached via Firewire, but I've
> since switched to USB, as our firewire subsystem is less than rock

Interesting. I find the reverse :)
Then again I started using Firewire in 4.x where USB2.0 didn't exist and th=
e=20
USB 1 code was kind of dodgy.

> The question really is, are 512 byte disk writes considered to be some
> kind of "atomic" as it is the smallest disk block size? What does the
> ATA subsystem do with writes of 4096? Are they completed atomically too,
> or not?

I think that in reality with a modern high capacity disk you don't get atom=
ic=20
writes at all because they all re-write whole tracks.

Yes this violates the assumption soft updates makes, I believe the only way=
=20
around it is to buy SCSI drives (not because they're SCSI per se, but becau=
se=20
they're smaller capacity so they don't do this)

=2D-=20
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C

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