Mystery writes to boot volume on 9.10.2 U1 and U2 - possibly linked to snapshots/replication

[PhilipS]

In disk reporting I am showing a consistent amount of write activity to the boot volume on 2 of my 4 systems.

The system dataset is not located on the boot pool on any of the systems.

System 1 is running FreeNAS-9.10.2-U2 (e1497f2) and shows 354MB written in the last 24 hours with 19k write IOs and 6k delete IOs (Attached IO graph)
System 2 is running FreeNAS-9.10.2-U1 (86c7ef5) and shows 878MB written in the last 24 hours with 59k write IOs and 10k delete IOs

The other two systems that don't show any activity are replication targets only.

Looking in the file system modified time, it looks like the writes are happening in /data/freenas-v1.db

On System 1, the write activity SEEMS to happen around 15 minute intervals which correspond to a 15 minute snapshot/replication
On System 2, the write activity is heavier and seems more random - also this system is under more load than System 1, but has similar 15 minutes snapshots/replications setup.

These systems are the Supermicro systems in my signature.

 

[SweetAndLow]

Rrd data being written to boot pool? You need to check that box in the GUI also.

Sent from my Nexus 5X using Tapatalk

 

[PhilipS]

Yeah, box is checked.

 

[PhilipS]

Okay, pulled the sqlite database at different intervals and ran an sqldiff on them and found that it is the replication that is causing the writes:

Code:

UPDATE storage_replication SET repl_lastsnapshot='auto-20170407.1745-1y' WHERE id=1;
UPDATE storage_replication SET repl_lastsnapshot='auto-20170407.1745-4w' WHERE id=9;
UPDATE storage_replication SET repl_lastsnapshot='auto-20170407.1745-1y' WHERE id=10;

Filed a bug for this: https://bugs.pcbsd.org/issues/23200

 

[PhilipS]

Just an update - not only was replication causing writes, but I found that SMB sharing using AD with Kerberos was writing to /.rnd

In my case, I would say 80% of the writes were related to Kerberos, the other 20% to replication.