Date: Tue, 11 May 2010 16:02:06 -0700 From: Chuck Swiger <cswiger@mac.com> To: George Sanders <gosand1982@yahoo.com> Cc: questions@freebsd.org Subject: Re: dumping a raid member with 'dd' for insurance... Message-ID: <82D375DD-9641-4602-93A9-5D84BB55688E@mac.com> In-Reply-To: <914660.33515.qm@web111619.mail.gq1.yahoo.com> References: <914660.33515.qm@web111619.mail.gq1.yahoo.com>
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Hi-- On May 11, 2010, at 3:35 PM, George Sanders wrote: > [ ... ] > I am planning on attaching each individual member of the raid5 array to a test FreeBSD system, and run: > > dd if=/dev/ad1 of=/data/disk/image.file > > Two questions: > > - is that a complete 'dd' command, or do I need to specify "bs=xxx" and "count=xxx" ? What you've suggested should work as-is. Adding the count option isn't useful, but specifying a bs of 64k or larger will considerably speed up the process of copying the data. Since you're dealing with a failed array and it's possible some of the disks might have errors when read, using conv=noerror might also be a good idea. > - is there any chance that simply booting with this drive attached to the system, and running a 'dd' like this, will somehow alter the contents or "touch" the array member in any way ? What I have described above appears to be a completely read-only process, but I'd like to make sure there aren't ANY bits that FreeBSD will write to this disk ... Many disks have a write-protect jumper which you can use to make sure no changes get written. Regards, -- -Chuck
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