[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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