This means the calculated parameters are not correct anymore, and you end up wasting a lot of memory for the metadata for a memory you don't have anymore. Now, if you boot up the system with dom0 having all the memory visible to it, and then balloon down dom0 memory every time you start up a new guest, you end up having only a small amount of the original (boot time) amount of memory available in the dom0 in the end.
First of all (dom0) Linux kernel calculates various network related parameters based on the boot time amount of memory.Instead set the dom0 memory to be something between 1 and 4GB adding dom0_mem=1024M to the Xen command line.ġGB is enough for a pretty large host, more will be needed if you expect your users to use advanced storage types as ZFS or distributed filesystems.ĭedicating fixed amount of memory for dom0 is good for two reasons: If the host has more memory than a typical laptop/desktop system, then do not rely on dom0 ballooning. Files: using files as backends for guest storage is not recommended for performance reasons, but it has several benefits in terms of features, like being able to use raw, qcow, qcow2 or vhd formats to store guests disks.The performance of iSCSI greatly depends on the capacities of the server and the network components, but if configured properly should provide a performance similar to LVM or ZFS. iSCSI: the default toolstack in Xen supports using iSCSI disks as storage backends for guests.Please note that due to ZFS memory requirements in this case the Dom0/Driver domain should be given at least 4GB of RAM (or even more in order to increase performance).
ZFS has some advanced features like ARC, L2ARC and ZIL that can provide much better performance than plain LVM volumes if properly configured and tuned. ZFS ZVOLS: this is a more advanced configuration, and should provide better performance if configured properly.LVM: this is probably the simplest way for obtaining good storage IO performance on Linux without much hassle.There are several choices for storage, however it is important to understand that the IO performance inside of the guest depends greatly on the storage option used: Tuning your Xen installation: recommended settings Storage options 2 Tuning your Xen installation: advanced settings.1 Tuning your Xen installation: recommended settings.