Re: silent semantic changes with reiser4

[Andreas Dilger]

On Aug 26, 2004  16:56 -0700, Hans Reiser wrote:
> Wichert Akkerman wrote:
> >UNIX doesn't have a copy systemcall, applications copy the data
> >manually.
>
> See sys_reiser4()..... ;-)  you can go "A<-B".  I have hopes of getting 
> drive vendors to support us in doing single disk copies without even 
> leaving the disk drive.....

Yes, we've wanted to have a "copy" syscall for a while now also, so that
Lustre (or other network FS for that matter) can do remote copies of
large files without having to go through the VM of the client.  The work
on sendfile() in 2.6 is a step in that direction, I eagerly await the
day when "cp" will try to do a sys_sendfile() call first, before doing
the read+write looping it does now.

Consider for a network filesystem we are limited to 1/2 of the client
network bandwidth (say 50-75MB/s) for copying instead of the server-local
or multiple server-server bandwidth for copies (400-600MB/s or more).

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://members.shaw.ca/adilger/             http://members.shaw.ca/golinux/

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