will 2 /home partitions mirror data?

JZL240I-U · 06-13-2007, 08:19 AM

Then use dd:

Code:

dd if=/dev/hdn | md5sum

might do the trick for a device. But /home is no device?!?

blackhole54 · 06-13-2007, 11:16 PM

Quote:

Originally Posted by len

i just ran df command for each /home device and they both report the same statistics- which leads me to believe that the drives are mirrored, and have the same data.

That's strange. My results (post #10) were just the opposite. When you check with df, are you mounting each partition individually, or do still have them both mounted at the same time?

BTW, you can certainly do an md5sum in the manner JZL240I-U suggested, but a mismatch would not necessarily mean that the essential info was not the same. That is because the md5sum would include all of the unused sectors in addition to the actual contents of the filesystem. It would also include things like mount counts and other such data.

JZL240I-U · 06-14-2007, 04:05 AM

Quote:

Originally Posted by blackhole54

...you can certainly do an md5sum in the manner JZL240I-U suggested, but a mismatch would not necessarily mean that the essential info was not the same. That is because the md5sum would include all of the unused sectors in addition to the actual contents of the filesystem. It would also include things like mount counts and other such data.

He could do a

Code:

dd if=/dev/zero of=/path/to/device/nullfile bs=1

As I understood from the previous posts, both disks are always simultaneously mounted but the file system data are a problem.

Like someone earlier posted, better use raid or rsync.

len · 06-15-2007, 10:33 AM

Quote:

Originally Posted by blackhole54

That's strange. My results (post #10) were just the opposite. When you check with df, are you mounting each partition individually, or do still have them both mounted at the same time?

BTW, you can certainly do an md5sum in the manner JZL240I-U suggested, but a mismatch would not necessarily mean that the essential info was not the same. That is because the md5sum would include all of the unused sectors in addition to the actual contents of the filesystem. It would also include things like mount counts and other such data.

blackhole, i did an md5sum as per JZL240I-U, and the md5sums didn't match. i ran the test 2 times, with one hdd reporting the same md5um, and the other a different one each time, both of which did not match. i'm led to believe that one /home is idled, and the other has processes ongoing that alter the md5sum (the md5sum test itself?). i'd have to archive, create an image, etc... of each /home directory, and/ or each hdd, and then md5sum the files to really see if what is stored is the same.

btw JZL240I-U, wouldn't "dd /dev/zero..." zero fill my hdd?

JZL240I-U · 06-18-2007, 01:10 AM

Quote:

Originally Posted by len

...btw JZL240I-U, wouldn't "dd /dev/zero..." zero fill my hdd?

No, it wouldn't. Note that dd is writing to an output file as per "

dd if=/dev/zero of=/path/to/device/nullfile bs=1". But this is just academic and in your case of no practical value.