Re: Why can't computers be simple?
- From: Mark Conrad <noneof@xxxxxxxxxxxxxxxxxx>
- Date: Thu, 21 Jun 2007 07:27:11 GMT
In article <tomstiller-1970C2.16171920062007@xxxxxxxxxxxxxxxxxxxxxxxx>,
Tom Stiller <tomstiller@xxxxxxxxxxx> wrote:
Concerning dd backup:
If everything works so flawlessly, why are you yammering away about
clearing the free space with zeros?
It does indeed work flawlessly, even better than the latest release of
"SuperDuper!" for example, as a Unix geek like you well knows.
I am "yammering away" about clearing free space (and file-system slack
cluster space) with hex zeros because of a nagging minor problem.
That problem is my present inability to create "small enough" compressed
backups, for emergency archive purposes; clearing free space will
eliminate that problem.
If you use a backup routine that's filesystem aware, it
doesn't matter what bit pattern is left in unallocated
sectors as they won't be written to the backup file.
Although dd can _copy_ the entire file system, dd can't _use_ the
file system. This means that dd has no way of telling where the files
end, and where free space begins.
That in turn means the entire Vista partition of 48 GBs has to be copied
by dd, not merely the 11 GBs of used files.
Interestingly, this copying of the entire Windows partition does not
need to be done with either Parallels or with a straight Mac partition,
because of the fact that I can jam _all_ files to end end of the
partition.
This allows me to copy just the files, plus a tiny safety margin of free
space, and ignore copying the great bulk of free space.
I can't do that jamming trick with a Windows partition created by
BootCamp, because Windows has those darn "immovable" files that do not
allow a defrag utility to jam all files to one end of a partition.
I'd like to hear how well you make out with daily backups
of those files that are changed in the course of a day's
productivity, assuming that you do anything which
warrants backing up the files.
That is easy, I look at the daily files to see whether any of them need
to be backed up. The large number of posts in this thread for example
do not need to be backed up, because nothing of value is being posted.
....except by me, of course. That example I posted about how deleted
files adversely affect compression was saved by me, because it took me
30-minutes to create that example file, by holding down the zero key etc.
Naturally I do not want to have to repeat that, should I have occasion
to repost that example in the future.
....and no, using /dev/zero would not fill the bill, because it would
not work with anything except hex zero.
Some day I am going to try /dev/0x30 just to see if that works.
If a "valuable" file occurs, I quickly throw it in a folder labeled
"Valuable Daily Backup". At the end of my computer session, I move that
folder to an external drive to await my next major dd backup.
Imagine how superfluous the Apple engineers working on
Leopard's "Time Machine" will feel when they learn of
Mark Conrad's marvelous 'dd' backup scheme.
Yep, especially when they realize that "Time Machine" will fail to
restore if any re-partitioning is inadvertently done.
Unlike Mark Conrad's marvelous 'dd' backup scheme, which can restore
after such a catastrophe.
Mark-
.
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