Hi There, We are working on our xen server setup... with two dom0 servers, one failing over to the other: My question is, how close to the dom0 servers need to be to run a domU on either? Do they need to be the same hardware type.. etc etc etc? Thanks Simon _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Matthew Palmer
2006-Jun-21 05:17 UTC
[Xen-users] Re: Hardware differences for 2 xen servers?
On Wed, Jun 21, 2006 at 04:27:52PM +1200, Simon wrote:> Hi There, > > We are working on our xen server setup... with two dom0 servers, one > failing over to the other: > > My question is, how close to the dom0 servers need to be to run a domU > on either? > > Do they need to be the same hardware type.. etc etc etc?Nope, because the dom0 provides a nice hardware abstraction layer. Basically, as long as they''re compatible architectures (ie you can have an x86 and an amd64 box, as long as everything''s running 32-bit userland) you shouldn''t have a problem -- so long as you''re running dom0s that are appropriate for the hardware, the domUs on top don''t care. - Matt _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Thorolf Godawa
2006-Jun-21 07:45 UTC
Re: [Xen-users] Re: Hardware differences for 2 xen servers?
Hi, >> My question is, how close to the dom0 servers need to be to run a >> domU on either? >> Do they need to be the same hardware type.. etc etc etc?> Nope, because the dom0 provides a nice hardware abstraction layer.this can be very wrong if you want to use (live)-migration! If you just want to start a VM, shutdown it later and restart it on the other server, the two machines can be different. But if you want to use such cool things like live-migration for s.th. like loadbalancing or maintanance between two servers they should be the same as possible. That doesn''t mean that the destination-server could not have faster/more CPU or more RAM, but the CPU and possibly also the chipset should be the same family! Otherwise it can happen during live-migration that on the source-system the CPU is in a status that is not compatible with the destination-system and the VM will crash. -- Chau y hasta luego, Thorolf _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Matthew Palmer
2006-Jun-21 10:19 UTC
[Xen-users] Re: Hardware differences for 2 xen servers?
On Wed, Jun 21, 2006 at 09:45:54AM +0200, Thorolf Godawa wrote:> >> My question is, how close to the dom0 servers need to be to run a > >> domU on either? > >> Do they need to be the same hardware type.. etc etc etc? > >Nope, because the dom0 provides a nice hardware abstraction layer. > this can be very wrong if you want to use (live)-migration! > > If you just want to start a VM, shutdown it later and restart it on the > other server, the two machines can be different. > > But if you want to use such cool things like live-migration for s.th. > like loadbalancing or maintanance between two servers they should be the > same as possible. That doesn''t mean that the destination-server could > not have faster/more CPU or more RAM, but the CPU and possibly also the > chipset should be the same family! > > Otherwise it can happen during live-migration that on the source-system > the CPU is in a status that is not compatible with the > destination-system and the VM will crash.Seriously? That sounds like a pretty bad failing of live-migration -- I''d *really* expect live migration to be robust against this sort of thing, otherwise you''d need to reboot the VM in order to put it onto upgraded hardware -- and if you''ve got to reboot it *any* time, then you have to design your infrastructure to accomodate that, and hence you have the capability to reboot it without service failure, so you don''t really need live migration after all... - Matt A little concerned _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Javier Guerra
2006-Jun-21 12:02 UTC
Re: [Xen-users] Re: Hardware differences for 2 xen servers?
On Wednesday 21 June 2006 5:19 am, Matthew Palmer wrote:> Seriously? That sounds like a pretty bad failing of live-migration -- I''d > *really* expect live migration to be robust against this sort of thing,the issue is that most OSs (at least Linux does it) detects some features of the CPU at startup time, and decides then if it wants to use them or not. for example, it might find SSE2 and use it for memcpys; later get migrated to a Celeron... and crash on the next call to memcpy migrating to ''bigger'' systems shouldn''t be a problem; unless you go from a 32-bit system to PAE, or 64-bit... -- Javier _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Tijl Van den Broeck
2006-Jun-21 13:40 UTC
Re: [Xen-users] Re: Hardware differences for 2 xen servers?
Live migration does indeed require a CPU from the same family (architecture and features) but afaik a different chipset doesn''t really matter. On 6/21/06, Matthew Palmer <mpalmer@hezmatt.org> wrote:> Seriously? That sounds like a pretty bad failing of live-migration -- I''d > *really* expect live migration to be robust against this sort of thing, > otherwise you''d need to reboot the VM in order to put it onto upgraded > hardware -- and if you''ve got to reboot it *any* time, then you have to > design your infrastructure to accomodate that, and hence you have the > capability to reboot it without service failure, so you don''t really need > live migration after all...It would indeed be nice if you didn''t have to reboot when moving towards a new architecture family but as you said... one has to design the infrastructure to ensure service continuity. I think HA-failover setups between domU''s (on seperate dom0''s) are most viable and live-migration is just a feature for small upgrades, for load balancing and it''s nice for showing off ofcourse ;-) _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 6/21/06, Thorolf Godawa <nospam@godawa.de> wrote> >> My question is, how close to the dom0 servers need to be to run a > >> domU on either? > >> Do they need to be the same hardware type.. etc etc etc? > > Nope, because the dom0 provides a nice hardware abstraction layer. > this can be very wrong if you want to use (live)-migration!> If you just want to start a VM, shutdown it later and restart it on the > other server, the two machines can be different.This is how we intend to use at this stage anyway. The server equptiment we are looking at is a IBM xSeries 336 for primary with dual HT Xeons and a xSeries 306m with with a single HT Pentium 4... RAID 5 on the primary, and RAID 1 on the fail over. This setup will run 1 domU for mail storage and processing and multiple domUs for pop/imap/smtp proxys and multiple apache/php/mysql domUs. These are setup for virtual ASP clients. Simon _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users