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Martin Baum 01-06-2010 10:00 AM

Optimizing dd images of ext3 partitions: Only copy blocks in use by fs

for bare-metal recovery I need to create complete disk images of ext3
partitions of about 30 servers. I'm doing this by creating
lvm2-snapshots and then dd'ing the snapshot-device to my backup media.
(I am aware that backups created by this procedure are the equivalent
of hitting the power switch at the time the snapshot was taken.)

This works great and avoids a lot of seeks on highly utilized file
systems. However it wastes a lot of space for disks with nearly empty

It would be a lot better if I could only read the blocks from raw disk
that are really in use by ext3 (the rest could be sparse in the
imagefile created). Is there a way to do this?

I am aware that e2image -r dumps all metadata. Is there a tool that
does not only dump metadata but also the data blocks? (maybe even in a
way that avoids seeks by compiling a list of blocks first and then
reading them in disk-order) If not: Is there a tool I can extend to do
so / can you point me into the righ direction?

(I tried dumpfs, however it dumps inodes on a per-directory base.
Skimming through the source I did not see any optimization regarding
seeks. So on highly populated filesystems dumpfs still is slower than
full images with dd for me.)

Thanks a lot,

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