[mythtv-users] Single partition or whole disk

Ramon Hofer ramonhofer at bluewin.ch
Tue Jul 3 09:01:29 UTC 2012


On Die, 2012-07-03 at 04:37 -0400, f-myth-users at media.mit.edu wrote:
> Btw, I've noticed that, when copying from a large local disk to
> another empty directory (e.g., when rsync is doing nothing but copying
> blocks), I often get much better performance by using "cp -a" instead.
> rsync doesn't seem nearly as efficient when the job is just "copy
> absolutely everything"; it uses significantly more CPU than cp, even
> though "just copy the file" should be the same amount of work in
> either.  I conclude that a lot more time was spent optimizing cp for
> its one task in life.
> 
> Of course, after that initial copy, rsync will be much faster, because
> it will only be copying new files or new pieces of files.  And I often
> do "cp -a" and then follow up with an rsync just in case I've missed
> something somehow; if there's nothing to do, it will be almost instant.
> 
> So if you've just started the copy, and you're impatient, try cp and
> see if your performance goes up.  (Might, might not, depends on
> whether you're bottlenecked at the disk, the disk interface, or
> on the CPU.  But 60 MB/sec is actually probably not as fast as
> these drives can go; I think I've seen higher transfer rates on mine.)


Thanks for the hint!

I've used rsync because it shows the progress. About the speed I had the
same feeling.
Here's a test:

rsync:
Recordings/5001_20120526133000.mpg
       5.04G 100%   63.95MB/s    0:01:15

cp:
time cp recordings/Recordings/5001_20120526133000.mpg
recordings_temp/Recordings/

real    1m12.981s
user    0m0.096s
sys     0m8.737s


Another reason why I used rsync is that it keeps the users and
permissions. But I now saw that cp does this too.


Cheers
Ramon



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