Zero offloading is similar to copy offloading, but while copy offloading is also available to Windows hosts, zero offloading is exclusive to VMware. Rather than require the ESX server to write zeros to storage blocks, such as when deleting a virtual machine, it can instruct the array to write those zeros for it. Again, the result is far lower ESX server CPU utilization and a quicker response.
Another VMware-only feature in version 5 is hardware-assisted locking. Normally, when VMware conducts certain operations -- such as powering a virtual machine on or off, executing a VMotion, creating a new virtual machine, or deleting a snapshot -- the entire VMFS file system is locked momentarily. When these actions occur sporadically, it's not much of a problem, but when there's a run on the VMware farm -- such as when a bunch of new VDI desktops are powered on -- it can create delays. In this new firmware version, EqualLogic arrays can lock only the blocks required to perform that operation, allowing the VMFS file system to continue to serve other requests. Thus, there are no delays felt by concurrent operations, which can help significantly when the file system is getting hammered.
Thin clones: Multiple volumes in one
Another new feature is thin clones, which provide the ability to clone a volume without consuming additional storage space. Thin clones can be made of any existing volume, though any volume used as a source for thin clones can no longer be accessed directly. The cloning process is very quick, as it's essentially creating a volume of pointers to the source, but otherwise thin clones function as any other storage volume. New data written to the clone inhabits its own space on the storage array, but reads from the cloned data come from the source volume.
Thin clones are ideally suited to use cases where a number of servers or desktops might share a common OS installation on a source volume, as the storage requirements for those systems become significantly smaller than dedicating a full volume to each. Thin clones also ease replication, as only the data written after the thin clone was created needs to be pushed to the replication partner.
Another use case might be large data sets found in development or read-only databases, where the source volume contains a fixed data set. A thin clone can be created for anyone who needs to work with that data without disturbing other processes that need to access or manipulate the same data.
Finally, a thin clone can subsequently be converted into a full volume, but that volume necessarily requires the full amount of space allocated to both the source volume and the data written to the clone itself.
EqualLogic Group Manager refresh
There are some cosmetic and usability changes in the new firmware as well, with the addition of quick-access view selection buttons in the bottom left of the EqualLogic Group Manager administration application. There's also context-sensitive help buttons, enhanced view modifiers, monitoring and event log updates, and a new alarms and operations bar at the bottom. While the overall look and feel of the GUI hasn't changed substantially, these new features are welcome and quite useful. Those with previous experience with the UI will find themselves right at home.
At the back end, there are other additions. EqualLogic has had support for Perl-based scripting through a telnet interface for a while now, and it has added support for Python scripting through an SSH-based interface. The two are exclusive, meaning you can't use Perl via SSH or Python via telnet, but providing the Python support does allow for broader, more secure scripting support.