% more space reqd. when dd is used?

[s.srinivas]

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hi all,

I have two  physical harddisks /dev/hda1 and /hdb

1) i want to copy drive (take backup) to a file ( in /hdb)using dd.
So how much space( in terms percentage)more is required in /hdb
for it to be copied successfully.

2) After copying using dd if=/dev/hda1 of=/hdb/backup

how to retrive it back again in terms of directories and sub-directories
and files.

thank u all

regards
vasu

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