Hi List, is there mathematical method to calculate how many VMs I can run on a single server? For example: in my setting I have one server with Intel Xeon 3050 Dual Core - single socket - with 4GB Ram and 2 hdd of 250GB SATA; hard drive is mirroring with software RAID and I''m using an image disk for xen VM. I want run only HVM vm. How many VMs can I run on this? Now I''m using RAM as delta (suppose to give 5-10 GB of disk space): if I give for each VM 256MB of RAM I will be able to start 14 domU with 90 - 100 MB of RAM in dom0. Is it right? Does anyone know another more accurate method? Thanks. Kind Regards. -- Alessandro R. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi Alessandro, On Thu, Aug 23, 2007 at 06:05:02PM +0200, Alessandro R. wrote:> Hi List, > > is there mathematical method to calculate how many VMs I can run on a > single server?No, since it depends on what resources the individual domains need. For example, my users tend to use more IO than CPU or RAM, so I always run out of disk spindles before I run out of disk space, RAM or CPU. Others may well have users that need a lot of RAM, or are CPU-bound, or whatever.> For example: in my setting I have one server with Intel Xeon 3050 Dual > Core - single socket - with 4GB Ram and 2 hdd of 250GB SATA; hard > drive is mirroring with software RAID and I''m using an image disk for > xen VM. I want run only HVM vm. > > How many VMs can I run on this?One, if it needs ~4G RAM and ~250G of disk.> Now I''m using RAM as delta (suppose to give 5-10 GB of disk space): > if I give for each VM 256MB of RAM I will be able to start 14 domU > with 90 - 100 MB of RAM in dom0.You will have no problem starting and running 14, 15, 20, 30, maybe 100s of domains. Whether they have enough resources to do what you want them to do is another question. Cheers, Andy _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
2007/8/23, Andy Smith <andy@strugglers.net>:> Hi Alessandro, > > No, since it depends on what resources the individual domains need. > > For example, my users tend to use more IO than CPU or RAM, so I > always run out of disk spindles before I run out of disk space, RAM > or CPU. > Others may well have users that need a lot of RAM, or are CPU-bound, > or whatever.Ok. So it''s a stitistic of usage. I have to see what the user do to calculate what is the best conf of each VM right?> > For example: in my setting I have one server with Intel Xeon 3050 Dual > > Core - single socket - with 4GB Ram and 2 hdd of 250GB SATA; hard > > drive is mirroring with software RAID and I''m using an image disk for > > xen VM. I want run only HVM vm. > > > > How many VMs can I run on this? > > One, if it needs ~4G RAM and ~250G of disk.:D> > > Now I''m using RAM as delta (suppose to give 5-10 GB of disk space): > > if I give for each VM 256MB of RAM I will be able to start 14 domU > > with 90 - 100 MB of RAM in dom0. > > You will have no problem starting and running 14, 15, 20, 30, maybe > 100s of domains.> Whether they have enough resources to do what you want them to do is another question.^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ I can''t understand this paragraph. Can you explain? thanks. regards. -- Alessandro R. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thu, Aug 23, 2007 at 07:07:24PM +0200, Alessandro R. wrote:> > You will have no problem starting and running 14, 15, 20, 30, maybe > > 100s of domains. > > > Whether they have enough resources to do what you want them to do is another question. > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > I can''t understand this paragraph. Can you explain?OK, well say you have a server with 4G of RAM, and you start 15 domains with 256M RAM each leaving 256M for dom0. Now you load an application on every domain that wants 512M of RAM. All domains run out of RAM, work entirely from swap, this causes massive disk IO across the whole server, load averages spiral upwards and probably the whole machine becomes unusable for all domains. You have to spec each domain like any other server.. Cheers, Andy _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users