An Uneasy Feeling

[Bob Farlow]

I have always had a uneasy feeling about defragging a system disk. There have been a few times when things just didn't work right after a long defrag session. I have always wondered if it would be possible for some of these backup programs like Acronis True Image to be written so that after you have made a image of a partition that was somewhat fragmented, it would automatically defrag the image as it being restored. Sounds to me like this would be a major step in the right direction. Let me know your comments,(even if you don't agree).

[Wiz Feinberg]

An Acronis disk image is a data file bitmap. A snapshot of the data on the hard drive is taken when the image is saved. Upon restoring the image the bitmap is reassembled as is. Acronis does not look inside the saved image to see if there is fragmentation.

Fragmentation occurs normally on any kind of hard disk as files are accessed. Data is recorded into sectors on the hard drive and those sectors become separated as other files and functions are accessed while the first ones are still open in memory, then written back to the disk. This causes fragmentation of the data. Eventually this leads to slowdowns as the seek mechanism works harder to gather the desired data into files again. I regularly defrag my system disk, after using Ccleaner to remove temp files and unneeded Windows Installer folders. A defragmented disk works more efficiently than a fragmented disk. Therefore, it produces less wear on the hard drive and seek arm to access files that are needed. A badly fragmented disk will wear out faster and all file reads and writes will be much slower than they should be.

In my opinion, if things don't work right after defragging, something has gone wrong with critical files and they may need to be repaired or reinstalled.

Someday we may have operating systems that don't cause fragmentation, but that day isn't here yet. Until it arrives you will need to defragment your system disks. This included the new SSD drives. It is the OS that causes fragmentation as it multi-tasks.

Here is a search page full of results about how Defrag works.

[John Cipriano]

Technically fragmentation is a property of the filesystem, but it's not always a problem. It's rare that ext3 needs a defrag. In fact I don't think there's an online ext3 defrag program, the fs just stores things intelligently.

Wiz, where did you hear that SSDs need filesystem defragmentation? I've only ever heard the opposite. They're not accessed sequentially, after all. And wear-leveling plus splitting the data along multiple channels means that something that looks sequential to the fs probably won't be anyway. And something that somehow actually was sequential would be bad for the SSD and bad for access times.

There is a sort of internal fragmentation that happens to the drive as a result of the erase block size being larger than the smallest writable block size. But the drive controller is supposed to take care of this. I'm certainly no expert though (and have yet to buy an SSD) so if you have a link or two I'd like to read more.

Bob: like Wiz said if defrag caused you a problem in the past, it wasn't strictly because of the defrag. It could have been a failing disk or a previously unnoticed problem. If your partition is fragmented (which it will be, they're never perfect) then the backup image will be too. But this is not really a big deal. It's just important that you have the backup. You could always defrag it once you restore if there were performance issues.

[Wiz Feinberg]

@John;
I recently read an article about fragmentation and tests were conducted on SSDs and they too became fragmented with use. However, since they respond much faster than mechanical drives, the fragmentation has less affect on data delivery speed. Defragmenting them may reduce their lifespan minutely, but not that much. The benefits outweigh the negatives.

It is the operating system and filing allocation table system (coupled with multi-tasking) that leads to fragmentation. If I am able to find that article I will add a link to in in a followup reply.

[Chip Fossa]

Wiz,

If I'm not mistaken, and it may have been Jack S.,
but someone told me with Vista, that defragmenting wasn't that much of an issue, as it used to be in previous renditions of Windows.

I posed the question after doing a defrag when I first got Vista, and noticed that the process moved along, I guess, but with no AUTHORITY. As in the past.

When you could physically see some kind of grid or scale movement to let you know about the progression of the defrag.

Vista defrag stinks. JMSHO