1:50 a.m.
Hello,
I'm testing an Oracle RAC with 2 Oracle Linux VMs inside a 4.0.6
environment.
They run on two different hosts
I would like to configure RAC intracluster communication with jumbo frames.
At VM level network adapter is eth1 (mapped to a vlan 95 at oVirt hosts
side)
At oVirt side I configured a vm enabled vlan with mtu=9000
I verified that at hosts side I have
vlan95: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000
ether 00:1c:c4:ab:be:ba txqueuelen 1000 (Ethernet)
RX packets 61706 bytes 3631426 (3.4 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 3 bytes 258 (258.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
And able to do a
ping -M do -s 8972 ip
from each host to the other one
In VMs I configure the same MTU=9000 in ifcfg-eth1
But actually inside VMs it works erratically: the same ping test is ok
between the VMs but Oracle checks sometimes work and sometimes give error
on communication.
At initial cluster config, the second node fails to start the cluster.
I tried 5-6 times and also tried then to set mtu=8000 inside the VMs,
supposing some sort of inner overhead to consider (such as 2 times 28
bytes) but nothing.
As soon as I set MTU=1500 at VM side, the cluster is able to form without
any problem.
I can survive without jumbo frames in this particular case, because this is
only a test, but the question remains about eventual best practices to put
in place if I want to use jumbo frames.
One thing I see is that at VM side I see many drops when interface mtu was
9000, such as
eth1 Link encap:Ethernet HWaddr 00:1A:4A:17:01:57
inet addr:192.168.10.32 Bcast:192.168.10.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:93046 errors:0 dropped:54964 overruns:0 frame:0
TX packets:26258 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:25726242 (24.5 MiB) TX bytes:33573207 (32.0 MiB)
at host side I see drops at bond0 level only:
[root@ovmsrv05 ~]# brctl show
bridge name bridge id STP enabled interfaces
;vdsmdummy; 8000.000000000000 no
vlan100 8000.001cc446ef73 no bond1.100
vlan65 8000.001cc446ef73 no bond1.65
vnet0
vnet1
vlan95 8000.001cc4abbeba no bond0.95
vnet2
bond0: flags=5187<UP,BROADCAST,RUNNING,MASTER,MULTICAST> mtu 9000
ether 00:1c:c4:ab:be:ba txqueuelen 1000 (Ethernet)
RX packets 2855175 bytes 3126868334 (2.9 GiB)
RX errors 0 dropped 11686 overruns 0 frame 0
TX packets 1012849 bytes 478702140 (456.5 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
bond0.95: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000
ether 00:1c:c4:ab:be:ba txqueuelen 1000 (Ethernet)
RX packets 100272 bytes 27125992 (25.8 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 42355 bytes 40833904 (38.9 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vlan95: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000
ether 00:1c:c4:ab:be:ba txqueuelen 1000 (Ethernet)
RX packets 62576 bytes 3719175 (3.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 3 bytes 258 (258.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vnet2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000
inet6 fe80::fc1a:4aff:fe17:157 prefixlen 64 scopeid 0x20<link>
ether fe:1a:4a:17:01:57 txqueuelen 1000 (Ethernet)
RX packets 21014 bytes 24139492 (23.0 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 85777 bytes 21089777 (20.1 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[root@ovmsrv05 ~]# cat /proc/net/bonding/bond0
Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)
Bonding Mode: fault-tolerance (active-backup)
Primary Slave: None
Currently Active Slave: enp3s0
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 0
Down Delay (ms): 0
Slave Interface: enp3s0
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 00:1c:c4:ab:be:ba
Slave queue ID: 0
Slave Interface: enp5s0
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 00:1c:c4:ab:be:bc
Slave queue ID: 0
Any hint?
Thanks in advance,
Gianluca