Re: [gentoo-user] Re: Fast checksumming of whole partitions

[meino.cramer@gmx.de]

Nikos Chantziaras <realnc@arcor.de> [10-06-05 10:08]:
> On 06/05/2010 09:39 AM, meino.cramer@gmx.de wrote:
> >
> >Hi,
> >
> >  this night dd copies the contents of my first
> >  1TB disk to my second 1TB disk (same Model).
> >
> >  (dd if=/devsda of=/dev/sdb bs=4096)
> >
> >  I want to verify, that the copy is identical.
> >
> >  I tried (or: I am still trying) to checksum
> >  the first disk with
> >
> >  whirlpooldeep /dev/sda
> >
> >  whch seems to work but is DAMN slow (in relation
> >  to checksumming 1TB in whole).
> >
> >  Is there any faster and reliable way to checksum
> >  whole paritions (not on "per file" base)???
> >
> >  Thank you very much in advance for any help!
> >
> >  Best regards,
> >  mcc
> 
> Constructing a checksum means reading every byte off the partition.  So 
> it's slower as a copy to /dev/null, never faster (because the checksum 
> calculation also needs time.)
> 
> So in order to determine whether it's really slow, compare the time 
> needed to dd the whole partition to /dev/null to the time needed for 
> checksumming it.  Then post the times here and an expert might then 
> tell whether this can be improved at all or not.
> 

Since the following is only some "info in between" I answer not one
of the last posting, which only means, that this post somehow is
related to this fred but not as a direct reply.

I downloaded the current "Parted magic" which 
- copies itsself completly to RAM if wanted and runs from there
  which gives you back the dvd/cdrom drive for other things.
- contains a lot of get-out-of-a-desaster-tools combined
  with tools to play low level games with harddiscs
- contains dcfldd (!).

With this and dcfldd I copied one 1TB WD10EARS disk on a SATA1
controller to another harddisk of the same model with this 
timings (sda ==> sdb):

real: 293m17.265s
user: 113m59.072s
sys : 64m6.605s

Checksumming the second disk while copying its contents to /dev/null
reveals this timnings (sdb==>null:

real: 253m57.517s
user: 113m51.988s
sys : 32m21.381s

Again: The transfer was via SATA1 and the disks were jumpered to use 
SATA1 speeds only.

Despite a lot of CRC-error reported via dmesg/kernel logs the copy
was identical to the original. As mentioned, I think the via pata
conflicts with via sata in earlier kernels, since I do not see
these messages with 2.6.34.00.

I will check for sdd on the Parted Magic iso and post later what I did
find.

Does anyone has experiences with gparted?
Is it recommended (I need support for ext4)?

Best regards,
mcc

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