For Windows systems, the traditional method to zero-fill free space has been to use the SDelete utility from Microsoft. However, SDelete comes with several limitations. It works by creating one large file that consumes all the free space on the disk. As a result, any applications or services on that disk must be shut down prior to using SDelete. SDelete is also resource-intensive and relatively slow, so whatever services or applications were on that disk will be unavailable until SDelete completes. Finally, SDelete is employed using a command line on a manual, disk-by-disk basis.
A Fully Automated Alternative to SDelete…
A fully automated alternative to SDelete is PerfectDisk’s Zero-Fill feature. PerfectDisk optimizes all the files on a Windows guest system and consolidates the free space into the largest possible contiguous chunk. It optionally zero-fills the consolidated free space offering several advantages over the SDelete utility.
First, PerfectDisk does not consume all the free space on the disk so applications can remain in use while it is running. Second, the zero-fill process can be scheduled to run standalone or after an optimization pass. The scheduling is just a few clicks in the Scheduling wizard; no scripting or messing with Task Scheduler is needed.
Aside from shrinking the virtual disk, PerfectDisk offers several additional benefits not available with SDelete. In any virtualized environment, there are several key performance metrics to watch:
- PerfectDisk reduces the number of IOPS processed by the virtualization layer and lowers the associated resource demand for CPU and memory.
- Since PerfectDisk reduces the total physical accesses to the disk, the latency improves.
- The combination of fewer and larger I/O means less hypervisor overhead and fewer physical disk accesses, so more work gets done per unit of time.
If a thin-on-thin environment is using a zero-detect SAN, the hardware will be able to recover the free space PerfectDisk zero-fills after the compaction of the virtual machine.