RE: [Xen-users] high availability iscsi and xen setup

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> > - Is a clustered filesystem required?
> 
> NOT required, but im testing another kind of such a setup. My receipt is
> to run XEN-Boxes with glusterfs as filebases-Diskbackend...
> 
> http://www.gluster.com/community/documentation/index.php/GlusterFS_and_Xen
> 
> first tests were impressive and performance was higher than iscsi, since
> im running ~60VMs over 10GBit-Nics, where the iscsi-targets were the
> bottleneck :-(
> 

That's the way the Microsoft literature recommends for Hyper-V on a SAN. They 
use VHD files on a shared filesystem. I guess because you can lock the entire 
VHD file you mitigate a lot of the performance problems of a shared filesystem 
as each host is using its own chunk of the filesystem holding its VHD file. I 
assume that 'dynamic' VHD's that grow on demand take a bit of a performance hit 
when they need to grow though.

I'm impressed that the performance is actually higher that raw iSCSI. Do you 
have an explanation for that? How is each host accessing the shared storage?

James

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