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Re: [Xen-devel] [PATCH] [XM-TEST] block device write verify test 2nd att

To: Ewan Mellor <ewan@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] [XM-TEST] block device write verify test 2nd attempt
From: Harry Butterworth <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 23 May 2006 13:35:35 +0100
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On Tue, 2006-05-23 at 12:40 +0100, Ewan Mellor wrote:
> On Tue, May 23, 2006 at 11:35:55AM +0100, Harry Butterworth wrote:
> > The only difference from the last version of the patch is that the minor
> > version number in configure.ac is incremented.
> > 
> > >From the patch:
> > 
> > +# This test imports a ram disk device as a physical device into a domU.
> > +# The domU initialises the ram disk with data from /dev/urandom and
> > calculates
> > +# the md5 checksum of the data (using tee as it is written so as to
> > avoid
> > +# reading it back from the device which might potentially mask
> > problems).
> > +# The domU is stopped and the md5 checksum of the data on the device is
> > +# calculated by dom0.  The test succeeds if the checksums match,
> > indicating
> > +# that all the data written by domU was sucessfully committed to the
> > device.
> > +
> > 
> > This patch also enables tee and fancy head in busybox on the ramdisk.  I
> > have tested the patch with both `make existing' where the tests run but
> > the new test fails because the ramdisk is missing tee and fancy head and
> > `make` where the test passes successfully.
> Why don't you use dd instead of head -c?

I tried using dd with a block size of 1 and a count of the right number
of bytes but the test was very slow.  I didn't want to assume a 512b
block size and I'm not very good at shell script so didn't manage to
work out how to do it better.

> Why don't you just fix the size of the datablock that you write to the
> ramdisk, instead of determining the current size of the ramdisk with cat
> /dev/hda1 | wc -c?

I wanted to test writing at the device limits.  Sometimes there are off
by one errors that mean you can't write the last sector of a block

cat | wc -c was the most robust way I could think of for getting the

> Ewan.

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