Re: server-side-copy: seems not to get used

On Tue, 24 Mar 2026 14:54:25 +0100
"Stefan G. Weichinger via samba" <[email protected]> wrote:

> Am 24.03.26 um 14:24 schrieb Rowland Penny via samba:
> > On Tue, 24 Mar 2026 13:50:03 +0100
> > "Stefan G. Weichinger via samba" <[email protected]> wrote:
> >> Does that tell me that server side copy works already?
> > 
> > Probably not :-(
> > 
> > I copied a 3.1GB .iso file into a share directory, this took approx
> > 51 seconds I then connected to the share and copied the .iso to a
> > new name with smbclient scopy, this took approx 15 seconds, or to
> > put it another way, it was faster.
> 
> I see ...
> 
> > scopy attempts to use server-side copy but if it fails it falls
> > back to using read then write.
> 
> Read that as well on the man page.
> 
> Now I am back to square one. Why isn't it enabled or used?

I have no idea, my share is on an ext4 filesystem using Samba 4.22.6
and I connected from Samba 4.23.5

> 
> I am comparing 2 shares now: the home of root is located on an
> internal RAID array while other shares are on a LUN on a SAN.

That could be part of the problem, I am connecting to a filesystem, you
appear to be connecting to a mount, so even though you are connecting
to a 'share', that share is actually a mount of a storage device that is
elsewhere, it all adds latency. It might also affect server-side copy,
who knows ?

> 
> Did that right now: "scopy" took 1:50 min now for that same file, on
> the share on the SAN. And I re-did the "cp in ssh" also:  1:01 min
> 
> I might packet capture stuff on my client, right? My smbclient should 
> send a request for "ssc" and maybe receive some "sorry, no".
> 
> But I don't have a clue so far what to filter for.
> 
> At least here I could use wireshark.
> 
> 
> https://wiki.samba.org/index.php/Server-Side_Copy#Filesystem_Support
> says:
> 
> "FSCTL_SRV_COPYCHUNK works with any filesystem backing the Samba
> share."
> 
> hmm
> 

The thing is, you are trying scopy and the file is being copied, but,
from what you have said, there is no sign of it being copied to the
client running smbclient and then back to the server under a new name,
this to me would suggest server-side copy is being used, just not as
fast as you would like.

Rowland

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