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[Xen-users] Some observations on live migration & solution solicitation


I am now testing XEN live migration on 3 physical hosts with XEN 4.0.1 pvops Ubuntu 10.10 (2.6.35-22). The kernel is compiled and built with default selections plus the support for ext4 file system as well as the support for network file system server. The three hosts are connected by one D-link gigabit switch (DGS-2205).

I find that:

1) If the 3 hosts are booted about the same time, the live migration is working. (Working in this sense means that the downtime is within 1 minute.) However, between any of the two hosts, the downtime is asymmetric. In one direction, the downtime is constantly short, measured by loss of 0-1 packets via ping command to the migrated guest domU. But, in the other direction, the downtime is long and unstable, measured by loss of 40-50 packets on average via ping command to the migrated guest domU. However, in some cases, which are not so often observed, the downtime can be as short as loss of 3-6 packets.  

2) If one host is rebooted later, then live migration to the rebooted host will not work. The migrated guest domU on the rebooted host will not respond to the keyboard through ssh connection.

3) I also tried regular migration. It seems that  the downtime gap between the regular migration and the live migration is marginal. I am wondering if there is some special requirements (kernel, hardware, etc.) for enabling live migrations?

My expectation (for proceeding to the next step) is to have low downtime between two hosts (loss of 0-1 packets) in both directions, and I understand that there should be some configurations required. So could anyone tell what my current problem might be? (I am new to this area, please forgive about my simple questions if any.)

Wenda Ni, Ph.D.
Dept. of Computer Science and Engineering
State University of New York (SUNY) at Buffalo

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