On Mon, Apr 28, 2008 at 08:59:46AM +0300, Shachar Shemesh wrote:
> Robin Lee Powell wrote:
> >
> > How about 73?  Surely not a block aligment.  :D
> >
> > dd if=/dev/urandom of=test_rand_wierd bs=1 count=73
> > cat test_rand_wierd test_long1 >test_wierd1
> > cat test_rand_wierd test_long1 >test_wierd2
> > cat test_rand_wierd test_long1 test_rand_wierd >test_wierd3
> >   
> All files begin and end the same way, so I'm not sure what you are
> trying to test here. 

That's because I mis-typed; the first one was:

cat test_long1 test_rand_wierd >test_wierd1

> Try this:
>
> dd if=/dev/urandom of=random1 bs=1024 count=16
> dd if=/dev/urandom of=random2 bs=1024 count=1024
> dd if=/dev/urandom of=pad bs=1 count=73
> 
> cat random1 random2 > before
> cat random1 pad random2 > after
> 
> Now see if rsync manages to save much when it has "before" and it
> needs "after" (or vice versa)

Made two copies, so I could do both:

sent 1049756 bytes  received 6229 bytes  2111970.00 bytes/sec
total size is 1064960  speedup is 1.01

sent 1048929 bytes  received 6271 bytes  2110400.00 bytes/sec
total size is 1065033  speedup is 1.01

So, no.

With larger files, it's better, but still not great:

dd if=/dev/urandom of=random1 bs=1M count=16
dd if=/dev/urandom of=random2 bs=1M count=17
dd if=/dev/urandom of=pad bs=1 count=73

cat random1 random2 > before
cat random1 pad random2 > after
cat random1 random2 > before2
cat random1 pad random2 > after2

sent 17841045 bytes  received 41226 bytes  5109220.29 bytes/sectotal
size is 34603008  speedup is 1.94

sent 17841118 bytes  received 41226 bytes  3973854.22 bytes/sec
total size is 34603081  speedup is 1.94

So about half the file is sent; presumably the random1 part.

And rsyncrypto does, in fact, do far better, fwiw.

cat random1 random2 > before
cat random1 pad random2 > after
cat random1 random2 > before2
cat random1 pad random2 > after2

rsyncrypto plain/before cipher/before keys/before backup.key  
rsyncrypto plain/before2 cipher/before2 keys/before backup.key
rsyncrypto plain/after cipher/after keys/before backup.key    
rsyncrypto plain/after2 cipher/after2 keys/before backup.key  

sent 81235 bytes  received 41296 bytes  35008.86 bytes/sec
total size is 34661412  speedup is 282.88

sent 81299 bytes  received 41296 bytes  49038.00 bytes/sec
total size is 34661476  speedup is 282.73

-Robin

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