Re: [Xen-API] Disaster Recovery of Xen XCP.

[Denis Cardon <denis.cardon@xxxxxxxxxxxxxxxxxxxxxx>]

Hi James,

> Over the past couple of weeks I've installed XCP onto a USB stick and have 
> built up my virtual data-center.  Now it would appear that the USB stick is 
> failing and I would like to recover rather than rebuild.
USB stick have very bad wear leveling, and you should avoid using them 
if they is not mounted read only (you can take a look at the debian live 
project to have system booting from usb mounted read only). Actually I 
toasted a few usb stick with basic io write pattern.
I used to have a few XCP servers on usb stick/CF cards, and I switched 
all of them no SSD because of disastreous wear leveling. Standard XCP 
servers I/O pattern is not very intensive, and USB stick should 
theoritically be ok, however in case of problem you can get intensive 
logging and your USB stick will be toasted in no time.
> The good:
> This first showed up last night and I was able to shut down my VMs (at least 
> partially) and power cycle the server to get XCP back up and running.
> Also good (I think) all of the VMs and their related storage is hosted from a 
> hardware RAID controller.
>
> Whether I install another USB stick or use a normal hard drive, the issue is 
> the same:
>
> How do I get my VM's recognized on a new install of XCP?
XCP metadata (which define VMs setup, network config and corresponding 
virtual disk) are written in a db on the XCP partition (which you lost 
with your toasted USB stick). You can setup a daily backup using 
xsconsole on your storage SR for disaster recovery. Alternatively, you 
can do a xe pool-dump-database through cronjob to have your metadata on 
your backup server.
> If I recall correctly, when I created the RAID array as a storage repository for XCP, it warned me that all 
> contents would be lost.  However I don't think I need to "create" the SR...I just need to 
> "import" the SR and then "import" the VM's.
>
> With that in mind...Surely there's an "export" option somewhere in XCP??
Your new XCP install has no clue of what is inside your SR. I don't 
remember the exact commands to introduce this existing SR to your new 
server, but it should be something like 
http://support.citrix.com/article/CTX121896 . Do backup first if you are 
not familiar with all that stuff.
Cheers,

Denis

> Thanks,
>
> James
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--
Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint Sébastien sur Loire
tel : +33 (0) 2.40.97.57.55
http://www.tranquil-it-systems.fr


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