[Samba] Samba4 provides high I/O load

[Anton Markelov]

I use sernet-samba package (version 4.0.9-6) on Debian 7. Samba configured
as additional AD controller. Samba process infinitely writes something to
disk and makes high I/O load:

Total DISK READ:       0.00 B/s | Total DISK WRITE:     204.37 K/s
TID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO>    COMMAND
140 be/3 root        0.00 B/s    0.00 B/s  0.00 % 58.45 % [jbd2/vda1-8]
4081 be/4 root        0.00 B/s  110.05 K/s  0.00 %  3.49 % samba -D

It is not logs, I think, because they relatively small.

/etc/samba/smb.conf

# Global parameters
[global]
    workgroup = DALSTRAZH
    realm = dalstrazh.localnet
    netbios name = SAMBA4K76
    server role = active directory domain controller
        server services = rpc, nbt, wrepl, ldap, cldap, kdc, drepl,
winbind, ntp_signd, kcc, dnsupdate, smb
        dcerpc endpoint servers = +winreg +srvsvc
    log level = 1
[netlogon]
    path = /var/lib/samba/sysvol/dalstrazh.localnet/scripts
    read only = No

[sysvol]
    path = /var/lib/samba/sysvol
    read only = No

lsof -p 4081 - http://pastebin.com/BZVuNyA2

mount

sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,relatime,size=10240k,nr_inodes=217587,mode=755)
devpts on /dev/pts type devpts
(rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,noexec,relatime,size=313936k,mode=755)
/dev/disk/by-uuid/b7ff5fd8-dc08-4b00-be23-6c9c91eecec5 on / type ext4
(rw,noatime,errors=remount-ro,user_xattr,commit=60,barrier=1,data=writeback)
tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
tmpfs on /run/shm type tmpfs (rw,nosuid,nodev,noexec,relatime,size=909660k)
rpc_pipefs on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw,relatime)

data=journal and data=ordered takes no effect.

On second server (with same configuration) i/o seems normal.

How to find file which causes this problem, and how to fix it?