[Samba] Avoiding constant HDD access

[Albert Berger]

On Wed, Nov 07, 2018 at 10:10:41AM +0000, Rowland Penny via samba wrote:
> On Wed, 7 Nov 2018 12:46:50 +0300
> Albert Berger via samba <samba at lists.samba.org> wrote:
> 
> > On Wed, Nov 07, 2018 at 08:54:11AM +0000, Rowland Penny via samba
> > wrote:
> > > On Wed, 7 Nov 2018 05:45:45 +0300
> > > Albert Berger via samba <samba at lists.samba.org> wrote:
> > > 
> > > > I'm running a Samba server on Raspbian and observing that Samba
> > > > during idle periods is constantly (every minute) writing to HDD
> > > > (maybe doing some journaling?) what causes the HDD to constantly
> > > > spin and never standby:
> > > > 
> > > > root at rpi:~# pidstat -dl 20
> > > > Linux 4.4.50-v7+ (localhost) 	11/07/2018
> > > > _armv7l_	(4 CPU) 
> > > > 04:10:08 AM   UID  PID   kB_rd/s   kB_wr/s kB_ccwr/s iodelay
> > > > Command 04:10:28 AM     0  832      0.00      0.20      0.20
> > > > 0  /usr/sbin/smbd -D 
> > > > 04:11:08 AM   UID  PID   kB_rd/s   kB_wr/s kB_ccwr/s iodelay
> > > > Command 04:11:28 AM     0  832      0.00      0.20      0.20
> > > > 0  /usr/sbin/smbd -D 
> > > > 04:12:08 AM   UID  PID   kB_rd/s   kB_wr/s kB_ccwr/s iodelay
> > > > Command 04:12:28 AM     0  832      0.00      0.20      0.20
> > > > 0  /usr/sbin/smbd -D
> > > > 
> > > > Is there some way (via configuration setting or maybe recompiling
> > > > with some parameter) to turn off this constant disk io?
> > > > 
> > > > /Al
> > > > 
> > > 
> > > At first glance it looks like something is trying to write to a
> > > share, but what is unclear from the info provided.
> > > 
> > > Can you post your smb.conf, without any commented lines and do not
> > > try to attach it to the post, all attachments are stripped by the
> > > mailing list.
> > > 
> > > Rowland
> > > 
> > > -- 
> > 
> > 
> > My smb.cnf:
> > 
> > [global]
> >    workgroup = WORKGROUP
> >    server string = Samba Server
> >    hosts allow = 192.168.1. 127.
> >    printcap name = /dev/null
> >    load printers = yes
> >    printing = bsd
> >    log file = /var/log/samba/%m.log
> >    max log size = 1000
> >    security = user
> >   username level = 6
> >   encrypt passwords = yes
> >   smb passwd file = /etc/samba/smbpasswd
> >   unix password sync = yes
> >   passwd program = /usr/bin/passwd %u
> >   passwd chat = *New*UNIX*password* %n\n *ReType*new*UNIX*password*
> > %n\n *passwd:*all*authentication*tokens*updated*successfully*
> > username map = /etc/samba/smbusers include = /etc/samba/smb.conf.%m
> >    interfaces = 127.0.0.1/8 192.168.1.0/24
> >    local master = no
> >    os level = 33
> >    domain master = no
> >    preferred master = no
> >    dns proxy = no 
> > 
> > [lib]
> > path = /mnt/lib
> > valid users = al
> > write list = al
> > read only = no
> > available = yes
> > browseable = yes
> > writable = no
> > guest ok = no
> > printable = no
> > locking = no
> > strict locking = no
> > directory mask = 0766
> > 
> > There are four more shares with similar settings.
> > 
> > When all client machines are disconnected from Samba server, the
> > Samba's idle io activity remains the same: disk write every 60
> > seconds. If this were a simptom of some failure, shouldn't there have
> > remained some trace in the logs? I checked /var/log/samba directory,
> > but there are no error reports in the last few days.
> > 
> > 'smbd --version' returns '4.2.14 - Debian'.
> > 
> > /Al
> > 
> > 
> 
> There isn't anything really wrong with your smb.conf, except these two
> lines in the share:
> 
> read only = no
> writable = no
> 
> 'read only' is an inverted synonym for 'writable', the first line says
> you can write to the share, but the second says you cannot. decide
> which you want and remove the other.
> 
> From the output of 'pidstat' you posted, Samba isn't trying to read
> anything from the share, but it is trying to write to the share, but
> the write is being cancelled, 'writable = no' ?????
> 
> Rowland
>
I tried in sequence to start Samba in following conditions:

1. With all clients disconnected from Samba server;
2. As above + all shares disabled;
3. As above + minimal smb.conf
4. With totally empty smb.conf.

In all cases those every-60-seconds writes persist.
What else can be done in this situation? Can it be
that some Debian/Raspbian patch causes this behaviour? 
Should I try to compile Samba from upstream?

/Al