Date: Wed, 09 May 2001 22:19:05 -0600 From: Chris Fedde <chris@fedde.littleton.co.us> To: Mike Meyer <mwm@mired.org> Cc: "PC Doc" <pc-doc@worldnet.att.net>, questions@FreeBSD.ORG Subject: Re: Use DD to make image copy of dual boot drive? Message-ID: <200105100419.f4A4J5801430@fedde.littleton.co.us> In-Reply-To: <15097.57945.106659.703869@guru.mired.org>
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On Wed, 9 May 2001 19:35:37 -0500 Mike Meyer wrote:
+------------------
| PC Doc <pc-doc@worldnet.att.com> types:
| > Is copying the whole disk, sector by sector doable with DD? What would the
| > command be? I think the 'c' partition refers to the whole disk so I would
| > guess something like:
| >
| > dd if=/dev/rwd0c of=/dev/rw1c bs=???
|
| I used to do backups - and run them - that way. On the other hand,
| that was a *long* time ago.
|
| > I'm not sure about the devices and what would be a good block size. Do I
| > need to use 512 bytes? The disks say: 32-bit mult-block-16 so that that me
an
| > an "efficient" block size would be 16x512? Or would a track (63x512) be
| > better?
|
| As long as it's at least 512 bytes, things should work. On the other
| hand, the bigger you make it, the faster the copy will go, unless you
| force your system to start swapping. I used to do half-cylinder
| chunks, because a full cylinder would cause the 11/70 to start
| swapping.
+------------------
Using one of the dis performance testers like Iozone or bonnie can help you
figure out the optomal block size for your system. I've found that about
4096 is optomal for my systems.
chris
--
Chris Fedde
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