[Samba] Samba and admin users performance

[Stijn De Smet]

Hello,

I have a performance problem when I don't connect using root and/or a user
in the "admin users".
Configuration:
Samba 3.5.11 running on SLES11SP1. The share exported is on a GPFS
filesystem and the GPFS vfs object is loaded(not loading it doesn't change
the described behaviour)
clients: Windows 7 and Windows 2008R2 all at latest update level.

[testshare]
        comment = testshare
        path = /testfs1/testshare
        read only = no
        force create mode = 0666
        force directory mode = 0777
        force security mode = 0666
        force directory security mode = 0777
        admin users = testuser


If I connect using a user other than testuser, I get ~8 MB/s from the
clients, and if I look at a trace, I can see that all read operations are
in 4K blocks(Read AndX Request/Response). If I connect using root or
testuser(which is in the admin users), I get 50MB/s and samba goes up to
60KB blocks when reading. Also during the negotiation, I can clearly see
that "Max Buffer: 0" is set in the "Session Setup AndX Request,
NTLMSSP_NEGOTIATE sent by the client, while this is 16644 when connecting
as root/testuser.
When switching to "security = share" and using guest access, I can see the
same behaviour. Setting force user/group to root gives good performance,
setting it to something else kills performance.

Is this expected, or am I missing something?

Best regards,
Stijn