InstaGENI Racks VM Resource Allocation

Memory allocation per VM

The default Xen VM memory allocation in an InstaGENI rack is 1GB for the default image. Each physical Xen server host has 48GB of memory, out of which 5GB is reserved for the Xen server host itself. From the remaining server memory, it is possible to allocate 43 VMs. Each standard InstaGENI rack has 3 VM server hosts, but racks can be configured to support additional servers. Currently the Utah DDC InstaGENI rack has 15 VM servers. The Virginia Tech InstaGENI rack will have 10 VM servers.

Disk Space Allocation

Each standard InstaGENI rack has 1TB of disk space available. Disk space is allocated on the InstaGENI racks as follows:

1. There is a disk image for each VM, which can be a user-created or a GENI/Emulab-provided image. The default GENI/Emulab provided compressed image requires less than 1GB of disk space. User-created images may be larger. When used, these images are cloned onto the space allocated to a VM.

2. The default Xen VM disk space allocation for each VM is 20GB. This allocation started at 4GB in early deployments, increased to 8GB and is now 20GB. The allocation has increased to accommodate many experimenters who want to run tools or generate logs that require lots of disk space. (Running out of disk space on a VM is fatal for the VM instance.)

3. Additionally the Logical Volume Manager (LVM) shares disk space with the WV disk images. Any new custom image loaded on the physical host server is mounted as a local volume from the same 1TB disk that stores all available images. This allows software to clone the new volume anytime a VM with the same disk image is requested. There is no reserved disk space for the LVM, so its size may vary across racks.