Proxmox VE 4.0 3-nodes (HP DL380 Gen8) cluster has been upgraded to 4.1
All VMs were stopped via disabled in HA before upgrade and all nodes were rebooted after upgrade.
All VMs were started by HA. All Ok.
I did load testing ceph-storage by two VMs placed on different servers and running the HDD-test program inside the each VMs.
After about 35-40 minutes GUI suddenly stopped working...
It turned out that there was a restart of the three servers...
In syslog (in all servers) was not found anything suspicious, sudden reboot only:

In iLO log the same:

How to identify the problem?
P.S.
# pveversion -v
proxmox-ve: 4.1-26 (running kernel: 4.2.6-1-pve)
pve-manager: 4.1-1 (running version: 4.1-1/2f9650d4)
pve-kernel-4.2.6-1-pve: 4.2.6-26
pve-kernel-4.2.3-2-pve: 4.2.3-22
lvm2: 2.02.116-pve2
corosync-pve: 2.3.5-2
libqb0: 0.17.2-1
pve-cluster: 4.0-29
qemu-server: 4.0-41
pve-firmware: 1.1-7
libpve-common-perl: 4.0-41
libpve-access-control: 4.0-10
libpve-storage-perl: 4.0-38
pve-libspice-server1: 0.12.5-2
vncterm: 1.2-1
pve-qemu-kvm: 2.4-17
pve-container: 1.0-33
pve-firewall: 2.0-14
pve-ha-manager: 1.0-14
ksm-control-daemon: 1.2-1
glusterfs-client: 3.5.2-2+deb8u1
lxc-pve: 1.1.5-5
lxcfs: 0.13-pve1
cgmanager: 0.39-pve1
criu: 1.6.0-1
fence-agents-pve: 4.0.20-1
All VMs were stopped via disabled in HA before upgrade and all nodes were rebooted after upgrade.
All VMs were started by HA. All Ok.
I did load testing ceph-storage by two VMs placed on different servers and running the HDD-test program inside the each VMs.
After about 35-40 minutes GUI suddenly stopped working...
It turned out that there was a restart of the three servers...
In syslog (in all servers) was not found anything suspicious, sudden reboot only:

In iLO log the same:

How to identify the problem?
P.S.
# pveversion -v
proxmox-ve: 4.1-26 (running kernel: 4.2.6-1-pve)
pve-manager: 4.1-1 (running version: 4.1-1/2f9650d4)
pve-kernel-4.2.6-1-pve: 4.2.6-26
pve-kernel-4.2.3-2-pve: 4.2.3-22
lvm2: 2.02.116-pve2
corosync-pve: 2.3.5-2
libqb0: 0.17.2-1
pve-cluster: 4.0-29
qemu-server: 4.0-41
pve-firmware: 1.1-7
libpve-common-perl: 4.0-41
libpve-access-control: 4.0-10
libpve-storage-perl: 4.0-38
pve-libspice-server1: 0.12.5-2
vncterm: 1.2-1
pve-qemu-kvm: 2.4-17
pve-container: 1.0-33
pve-firewall: 2.0-14
pve-ha-manager: 1.0-14
ksm-control-daemon: 1.2-1
glusterfs-client: 3.5.2-2+deb8u1
lxc-pve: 1.1.5-5
lxcfs: 0.13-pve1
cgmanager: 0.39-pve1
criu: 1.6.0-1
fence-agents-pve: 4.0.20-1
