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Re: [Xen-users] Xen, LVM, DRBD, Linux-HA

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen, LVM, DRBD, Linux-HA
From: "Daniel Asplund" <danielsaori@xxxxxxxxx>
Date: Wed, 23 Apr 2008 23:54:31 +0200
Cc: Tom Brown <tbrown@xxxxxxxxxxxxx>
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Sorry, managed to send the mail by mistake...

I am using the latest stable version of Debian, 4.0. I compiled Xen 3.2.0 from source as well as DRBD 8.2.5.

At first I also thought I had performances issue as Samba was acting very weird. Copying a new file to my samba share went without problem(speed of 7-8MB/s) over a 100Mbps link, but when I tried to copy the file back just a few seconds later I had terrible performance. But I am sure this is an issue only related to samba.

With FTP in different directions and from different hosts I have perfect transmissions. From one VM to a standalone Linux box I reached speeds of 11MB/s, both transmit and receive.

Running hdparm -t on the device gives me same performance from within the VM as running it from the physical node. I have readings of 89-91MB/sec.

Will continue testing, especially getting samba to work properly, but so far I am very happy with this setup.



I get the impression that you want to run Linux-HA inside of the VM. Why not
put it on the Dom0 in your two physical nodes and have them control all your
VMs? Have you considered that or is it not fulfilling your needs?
I have a setup like that with two physical nodes. For each VM I create the
needed LVMs, same size on both nodes. I create a DRBD resource for each LVM

can I ask what you're using for a dom0 distribution? I've done this (without the HA stuff), but recently tried to do it with the default centos 5.1 kernels and drbd modules, and disk I/O performance went through the floor :(  it was fine with a homebuilt 0.7 drbd module, but with the centos 0.8 and 0.8.2 modules it sucked.

Unfortunately, the 0.7 module was implicated in at least one system crash and there were several with short uptimes, so I quit using that... and with the .8 and .82 modules having horrible performance I was forced to quit using drbd at least temporarily.


to have the data mirrored between the two nodes. Have each VM configured to
use its DRBD resources. Have heartbeat install on both nodes that controls
fail over of all VMs.

Live migration works for all para-VMs but not for HVMs. With HVMs I use
heartbeat to shutdown it down before starting it on the other node.

Cheers, Daniel

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