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Virtual Machines

Overview

Research Computing offers hosted virtualized servers for groups requiring dedicated systems. Virtualization helps avoid the cost of investment in dedicated hardware where raw horsepower or highly computational usage is not a concern. This document aims to outline our offerings and the levels of support offered on the various tiers.

TIERDESCRIPTIONADMINISTERED BY
1Fully monitored, RC is responsible for service availability and proper functioning. No sudo/root access. NFS mounts allowed.FAS RC
2RC provisions requested OS, end-user has limited privileged access (example: May have sudo to restart webserver). NFS mounts allowed.FAS RC & Customer (limited)
3RC provisions "bare metal" with requested OS, hands off to requester who gets full administrative privileges. No NFS mounts allowed, as a result. RC is responsible for proper functioning and health of the container and KVM infrastructure. End-user is responsible for all other maintenance including software and administration of services.Customer

Technology

Research Computing, where ever possible, make use of freely available opensource technologies. This helps us keep costs down, for ourselves and for our users, allowing us to offer service such as this for little to no cost. This also helps us avoid vendor lock-in, as well as fully understand our software stack and make our own customizations and fixes as needed.

To this end our virtualization infrastructure is currently based on KVM (http://www.linux-kvm.org/page/Main_Page) and LibVirt (http://libvirt.org/). These technologies allow us to quickly provision new systems on a on-demand basis, as well as clone and migrate them (live) between hosting systems (hypervisors).

Standard Offering

While we strive to be as flexible as possible, so that your group's needs can be satisfied, we do have a default base configuration. This allows us to have a full understanding and control the systems while offering the best support possible. As configurations drift away from this standard default, they become more and more "unique snowflakes" that require extra special care and attention.

Virtual Machines are suitable for many applications and usage models, but are not suitable for use as compute nodes, database or other disk intensive services, or computational/visualization nodes. Please contact us to discuss how best to implement those services for your lab or group.

Our default offering consists of a modestly configured VM, well suited to most low-to-mid end tasks. These systems are:

  • OS: CentOS 6.x
  • Virtual CPUs (VCPU): 1 - 2
  • RAM: 2GB
  • Networking: 1x1GB static network address, public IP addresses available as requested.
  • Disk: 20GB.

We have found that for most tasks, these specs are suitable, and this smaller footprint allow us to efficiently host many VMs in a small amount of space with very little power consumption.

VCPUS and RAM can both be extended, with in reason. Research Computing staff individually will make the call at which point a dedicated system would be best as RAM and VCPU need grow.

For disk storage, our approach is to keep disk images as small as possible, for maximum flexibility and efficiency (the bigger they are, the harder they are to move around quickly as things change). Smaller disks also allow VM backups to happen in a timely manner. Obviously not all applications/use cases can be satisfied with a 20GB disk which includes the OS. When this is the case our preferred path it to expose network storage (many times Shared Lab/Group storage, or storage specifically provisioned for this service) for additional capacity (see Tier table above for exceptions).

Backups of VM disk images/configurations happen nightly, and 2 weeks of history of these is retained. That being said, it is much easier/effective to restore from backups of network shared storage(it is more granular, with the VM disk image, the entire disk would have to be restored, not simply a part/section of it), and is yet another reason we encourage small disk images with network shared storage for data.

We can be flexible

The above default offering is simply that, the default. As always we are here to work with you and your needs. If different system specs are needed, more advanced networking configuration or a different OS, backup history length, or any special software needs, we can normally accommodate the special request(s).

As always, please contact us with any questions about VM hosting: RC Portal or email rchelp@fas.harvard.edu

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