Re: [Xen-users] Best Practise for Xen in "clustered" Environment

["Tijl Van den Broeck" <subspawn@xxxxxxxxx>]

On 5/2/07, Stephan Seitz <s.seitz@xxxxxxxxxxxx> wrote:
> Hi listmembers,
>
> we're currently using Xen (3.0.4) on some dedicated Machines. The DomU's 
> root-fs as well as
> the swapspace are located on the particular machines on lvm (single pv on 
> hardware raid).
>
> As we are running a lot of dedicated machines which could also get xenified, we 
> assume it's
> not the best practise in Installing a Xen "island" on every single machine.
>
> One solution we thougth about was, putting the lvm space which is available on 
> every single
> machine together via gfs, gnbd or similiar and let the domU's run from a 
> netwide available lv.
For a single box for all the servers, the most viable (and supported)
options are:
- Novell SLES with EVMS + OCFS
- Red Hat with CLVM + GFS

If you run Debian/Ubuntu/Gentoo/... you can go any direction you want.

As for sharing across the machines iSCSI is fully supported by Novell
& RH. So no need to use ndb (I doubt that's supported). That said for
one machine....

However, you want it from every node combined? I would not recommend
that in any way whatsoever.
One could indeed accomplish this by exporting every disk/LVM to
everywhere and thus making everything available everywhere. But in
that case, you might as well stick with the Island scenario, as "live
migration" would mean nothing, if you have to bring down a physical
node you'll bring down the original storage box of a domU as well so
it dies anyhow.
If only ZFS would be mainstreamed by now in the kernel you'd have a
very manageable option there.

> There are about 10-15 Machines available, each of them with at least 2 GBit 
> NICs, Hardware Raid
> (3ware and areca) with useable capacity from 400G upto 2T. Architecture is from 
> x86 (P4 HT
> without VT) upto x64_64 (EMT, Dual Xeon Dualcore with VT), RAM is probably an 
> issue, because some
> of the older machines doesn't support more than 4G); there are also some 
> equivalents equipped
> with AMD Processors (Dual Opteron with VT (the AMD equivalent, i think this is 
> called pacifica))
>
> The DomU's should only run x86_32 and don't need to be fully virtualized. 
> Paravirtualization should
> always be enough (or even better).
>
> We're currently really unsure, if this is in general a good idea, also if it's 
> practical, how would
> you get the lvm space together, as there are uncountable different 
> possibilities ?
> I would like to see, how you would do (or leave) this?
>
> A SAN/NAS solution is not possible, as we want to consolidate currently 
> available hardware. Bying
> new storage space is a no-go. Well, relatively low-prized equipment like 
> additional NIC's or RAM
> shouldn't be a problem. The currently installed "internal" switch is capable of 
> any kind of port
> truncing, qos and vlan on GBit, so network speed shouldn't be such a problem. 
> FC isn't availabe.
>
> If you've an ideas, I would really like to hear from you.
>
> Thanks in advance!
>
>
> --
> Stephan Seitz
> Senior System Administrator
>
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