Product Review: Diskeeper V-Locity 3

I'm a firm believer in the necessity of disk defragmentation. While some people maintain that solutions providing "always on" defragmentation areunnecessary in modern OSs with large amounts of RAM and intelligent caching of commonly accessed files, I've found that these programs turn a fastcomputer into one that's snappy. Although this isn't a night-and-day difference, it's an improvement that some users are prepared to pay for. Despitethis, I've had a long-standing love-hate relationship with Diskeeper software. Only with the release of Diskeeper 2011 and its inclusion of theEfficient Mode have I been truly satisfied that the program isn't constantly chugging away at my disks aiming to maintain a perfectlydefragmented state at all times, which is indeed unnecessary.

Many servers now utilize virtualization of one kind or another. File caching isn't optimized to work with virtualized workloads and it's unlikely thatthere's ever going to be enough RAM, so raw disk performance comes back into the spotlight. Based on the same defragmentation engines as Diskeeper2011, V-locity runs on Hyper-V host servers, providing local disk and SAN defragmentation. During the defrag process, it monitors agents deployed onthe guest virtual machines (VMs) to ensure there's no contention for disk resources. V-locity requires a separate Windows VM (or physical device) torun the host software in VMware virtual infrastructures.

V-locity supports Windows XP SP2 or later and Windows Server 2003 or later guest OSs on Hyper-V and VMware ESX/ESXi 4.0 or later hosts. VM guests arealso supported in Citrix XenServer.

Installing V-locity

My test system consisted of Hyper-V running on Windows Server 2008 R2 with a collection of Windows Server guest VMs. I found that installing the hostsoftware is straightforward and includes a warning that Windows Firewall settings might need to be modified if Diskeeper Administrator will be used tomanage V-locity.

When installing the V-locity guest software on a VM, you have two additional options to configure:Enable Automatic Defragmentation on all volumes on this computer andEnable Automatic Space Reclamation on all volumes on this computer. Both are enabled by default.

Understanding the Technologies

V-locity uses a variety of technologies to defrag physical and virtual disks. IntelliWrite replaces NTFS write logic to minimize defragmentation asfiles are written to disk. To avoid interfering with SAN optimization, Instant Defrag cleans up any fragments that occur while the write is still inprocess. InvisiTasking ensures that any defrag activity happens using idle processor cycles, while CogniSAN and V-Aware monitor VMs on local disks andSANs to ensure that there's no contention for resources as guest VMs defrag their local disks.

V-locity is able to detect different types of Virtual Hard Disks (VHDs), optimizing defrag routines to minimize unnecessary disk growth. Spacereclamation works in conjunction with live migration tools to compact VHDs during the migration process. V-locity automatically zeros out unused datablocks on VHDs so that Automatic Space Reclamation can run while a disk is online. VHDs can also be compacted manually if they're dynamic (orthin in VMware terminology) and offline. Finally, I-FAAST organizes files on the disk to provide the fastest access to frequently used files.

Using V-locity

Once installed, you probably won't touch the management interface very often, apart from the occasional need to compact VHDs. One disadvantage is thatyou must log on to each guest VM to perform management tasks, as there's no centralized view from the host server. Finding your way around themanagement console is intuitive, with all the discovered disks listed at the top of the window and statistics on current operations and performance ofthe defragmentation engine shown below. On the host server, the management interface lists all guest VMs on which V-locity has been installed (seeFigure 1), which is a comforting indication that the software is able to detect disk usage across all the virtual systems.

 
Figure 1: V-locity host management interface

V-locity reported a 34 percent I/O improvement after installation on my Hyper-V host. You can generate reports for individual disks by clickingAnalyze. This report contains detailed information about a disk's current state and performance.

A Low-Cost Performance Boost

The best thing about V-locity is the price. It's licensed per CPU on the host with an unlimited number of VMs. Despite the software's managementshortcomings, at this price it's a no-brainer. Diskeeper Administrator can be licensed at an additional cost if you need to manage a large number ofV-locity hosts. Smaller shops can probably survive without the extra management functionality because V-locity largely does its stuff without the needfor constant monitoring.