[DRBD-user] 8.3.11 on RHEL 5.7 w/ MTU of 9000 fails

Andreas Hofmeister andi at collax.com
Sat Jul 23 22:25:48 CEST 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On 23.07.2011 21:54, Digimer wrote:
>
> Thanks for the reply Andy.
>
> The hardware (Intel Pro1000/CT NICs[1] and a D-Link DGS-3100-24[2]) 
> both support 9kb+ frames (and JFs are enabled in the switch). With the 
> MTU on either node's DRBD interface (eth1) set to 9000, I confirmed 
> that JFs worked using a method very similar to what you suggested:
> >
> > --- an-node07.sn ping statistics --- 1 packets transmitted, 1
> > received, 0% packet loss, time 0ms rtt min/avg/max/mdev =
> > 0.686/0.686/0.686/0.000 ms ====
> >
> > node2: ==== [root at an-node07 ~]# ifconfig eth1 mtu 9000
> > [root at an-node07 ~]# ifconfig eth1 eth1 Link encap:Ethernet
> > HWaddr 00:1B:21:72:96:F2 inet addr:192.168.2.77 Bcast:192.168.2.255
> > Mask:255.255.255.0 inet6 addr: fe80::21b:21ff:fe72:96f2/64
> > Scope:Link UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1 RX
> > packets:30593 errors:0 dropped:0 overruns:0 frame:0 TX packets:26756
> > errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000
> > RX bytes:31161397 (29.7 MiB) TX bytes:30838239 (29.4 MiB)
> > Interrupt:17 Memory:feae0000-feb00000[root at an-node07 ~]# clear; 
> tcpdump -i eth1 icmp
> tcpdump: verbose output suppressed, use -v or -vv for full protocol 
> decode
> listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
> 15:45:10.474134 IP an-node06.sn > an-node07.sn: ICMP echo request, id 
> 11554, seq 1, length 8908
> 15:45:10.475236 IP an-node07.sn > an-node06.sn: ICMP echo reply, id 
> 11554, seq 1, length 8908
> ====

Ah. The '-Mdo' argument to ping just spares you the 'tcpdump'.

> 1. 
> http://www.intel.com/products/desktop/adapters/gigabit-ct/gigabit-ct-overview.htm
> 2. http://dlink.ca/products/?pid=DGS-3100-24

Mhh, I have a peer of nodes - actually with DRBD 0.8.11, not 0.8.10 as I 
thought - and Intel 82571EB NICs working rather well, but then these are 
connected back-to-back.

We had some bad experience with a D-Link switch in the past. Don't 
remember the model, but we eventually scraped it because of the troubles.

If you use pacemaker+corosync, you may want to check the "netmtu" 
setting in "corosync.conf". That should not affect DRBD though.

Ciao
   Andi
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