Automatic Defragmentation: The Pros and Cons

 

 

There seems to be a debate developing about the merits or demerits of automatic disk defragmentation. Automatic defragmentation is when defrag software (or a monitor) runs continuously in the background.  When the system has idle resources available, the software defragments the disk. Even when the defragmenter isn’t defragging some form of monitoring must occur to detect when the system is idle. This monitoring also consumes some resources. The discussion here is really about how much fragmentation is too much; and what is the best approach to eliminating that fragmentation. To explore the pros and cons here, we’ll look at how this might affect workstations, laptops and servers.

 

For organizations whose policy is to leave workstations on all the time, there could be an advantage to automatic defragmentation.  There may be plenty of idle time after employees leave for the day. Given enough time, the defragmentation should be complete. The same would be true if you used a screen saver defragmentation mode. If the organization requires systems to be turned off during non-work hours, there can be considerable downside to automatic defragmentation. The defragmentation may never happen in automatic mode because the systems are busy during the day.

 

 Laptop users are often a bit compulsive about system performance; any process that runs continuously is usually viewed as a negative. Of course, laptops are usually on when the user needs to use it. As a result, the amount of idle time on a laptop would be limited; so automatic defragmentation does not seem a natural fit here. In any event, you certainly would not want to defragment while you are running on battery power.

 

Servers represent an entirely different situation. Servers run 24 x 7 and system administrators typically do not want to take them down for anything other than routine maintenance. It would seem this might be the ideal environment for automatic defragmentation. From the defragmentation software vendor’s perspective, we would love to believe that system administrators around the globe recognize fragmentation as one of the main causes of server slowdowns and poor I/O performance. Our experience tells us otherwise. Most system administrators exhibit a very human behavior in that they are far more reactive than proactive. Once fragmentation is recognized to be a problem (and it will), they will look for a solution. The problem is that by the time fragmentation is an issue, you need something that makes the problem go away fast. Automatic defragmentation may eventually resolve the problem, as it chips away at fragmentation during system idle time. However, on a busy server there may be very little system idle time. The system administrator has no idea how long it will take the automatic defragmentation to defragment the disk.

 

Since the automatic defragmentation defragments files when available resources permit, the system administrator needs to consider an interesting dilemma while waiting for the disk to defragment. Will users create new fragmented files faster than the automatic defragmenter can defragment?  If the server is busy and the starting free space is fragmented, it is very likely that new fragmentation will happen faster than the automatic defragmentation can fix it.

 

 Raxco first offered automatic defragmentation in PerfectDisk Rx Suite, a consumer product we launched last spring. A slightly different version will be available in the new release of PerfectDisk coming soon.  We will continue to offer a robust scheduling option for those who want to know exactly what is happening and when it is happening. PerfectDisk users can choose between one time, daily and weekly schedules plus the very popular screen saver mode. A scheduled defragmentation provides the absolute certainty that the defragmentation gets done. That means the system, metadata and data files are contiguous, files that change infrequently are moved out of the way, and the free space is consolidated so refragmentation is slowed.

 

Automatic defragmentation may be just the ticket in some environments. The choice is between something that is always running; and something that runs as scheduled. The second choice is between the uncertainty of how long it will take to fix the problem; and knowing exactly when it got fixed. With PerfectDisk you have the flexibility to pick either option.