There is a monitor in OpsMgr that runs on a periodic basis (Every Saturday at 3 a.m. by default) to check the fragmentation levels of all logical drives. If fragmentation levels are found to be above threshold then by default the state of the monitor will change to “Warning” and an alert will be generated. There is a recovery named “Logical Disk Defragmentation” targeted to this monitor, which is disabled by default. If the recovery is enabled then the state change will automatically kick off a task to defragment the logical drive.
The OpsMgr rule can be tailored for any decisions that may follow. We can include/exclude drives from the check , optionally we can automatically execute a defrag job when an alert is raised.
Keep in mind – if this recovery rule is turned on it will defrag all physical boxes which will not be a big deal… it will simply fix the fragmentation issue. However – this will also run against VM’s which will also fix the problem however If this was triggered all at the same time – Saturday at 3:00AM by default – this can kill the disk I/O on the disk subsystem hosting your VM/VHD files.
We can also disable the rule altogether. The question is what is the strategic approach on disk fragmentation? Do we defrag some, all or do nothing. If it is that we are going to defrag some then a decision is to be made regarding which tool to use. Windows native defrag tool, third party app or other? .
The statement below articulates the very question of what to defrag.
“Windows administrators have had varied opinions about server disk defragmentation. Simply speaking, defragmentation is a good thing. Unfortunately, you cannot apply that blanket statement for all server implementations due to timing, data makeup, volume size, performance, or overpowered hardware.
· There are four main ways that administrators currently perform disk defragmentation:
· Do nothing
· Run defragmentation tool or command as needed
· Create a scheduled task
· Install a third-party tool to manage disk defragmentation and perform cleanups as needed
Windows Server 2008 R2 now includes a scheduled task to defragment all local disks. For organizations that want defragmentation to run in an automated fashion, the default Windows task is good enough for most implementations. More feature-rich defragmentation configurations will gravitate toward a third-party tool such as Diskeeper 2009, which offers superior configuration options to manage the defragmentation of disks, including optimizations for SAN and remote drives.
Shared storage and virtual machine usage are additional points that need a detailed review for each implementation as well. In this configuration, timing can be incredibly important, as a serious risk exists for a number of systems running a defragmentation on the same physical drive array or cabinet across simultaneously.”