[Samba] Very slow samba performance on Centos 6

[vg_ us]

Hello all,

I have 2 identical Dell r510 servers with 10gig card, running centos 6 with 
samba-3.5.4-68.el6_0.2.x86_64.
I setup 16G ramdisk samba share on both and ran cp from local ramdisk to 
samba ramdisk mount.
If I cp 12 1-gig files, I get combined 100MB/s transfer rate. Single file cp 
maxes out at about 15MB/s.
Ftp transfer give me over 300MB/s.

Running with 9000 MTU. Most smb.conf is default. I even disabled atime and 
tried ext2 and xfs on ramdisk.

Any help will be greatly appreciated.

- Vadim