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Showing posts from May, 2009

IET to ESX multipathing FAIL

A software-implemented iSCSI initiator (in VMware ESX) on one side, the iSCSI Enterprise Target (IET on CentOS5) software on the other side, and a separate storage VLAN to connect the two. Works great in my test lab.

But then I wanted to add multipathing to the setup. Plan was: create a second VLAN, and give both the IET server and the iSCSI client a new interface in that VLAN, using a new IP subnet. That gives the client two ways to reach the server, thereby introducing multipathing !

Unfortunately, IET spews error messages at high speed when doing this: I got "kernel: iscsi_trgt: Abort Task (01) issued on tid:1 lun:0 by sid:26459747326427648 (Unknown Task)" about 4000 times per second.

Restarted everything without the second storage VLAN and without the new interfaces, and now all is well again.

Link aggregation between CentOS 5 and a SLM2024

It's been a while since I made time to try something new. This week, I finally took something off of the "need to try this" list: link aggregation. I've had a gigabit Ethernet switch with link aggregation for about a year now, and my main Linux box has 3 gigE NICs, but I was still only using one. Time for change.

Google found me some good documentation for channel bonding on CentOS5. Manually editing the ifcfg-eth{0,1,2}, ifcfg-bond0, and modprobe.conf is all that's required. That worked, but the default bonding setting is "balance-rr", the simplest loadbalancing algorithm. What I wanted to use was full IEEE 802.3ad link aggregation, mode 4 of the bonding module.

During testing, I got fooled into believing that "service network restart" unloaded and reloaded the bonding module. It doesn't, I should have tested using "service network stop; rmmod bonding; service network start" from the start. Learned my lesson, configured the switch…