07-08-2012 11:52 PM
A couple of days ago I tried an admittedly fairly ambitious overnight free space bleach across my hard drives, which are divided into four nominal drive partitions (C:\ thru F:\), in total about 300 Gb., average utilization 60%.
When I came back to the computer (PC, Windows XP Home, SP3) the next morning Norton Utilities was no longer running. A check of the "System Health" status showed C listed against "Bleach Free Space".
Later that day, however, the system indicated that it was nearly out of space on drive C:\, which is usually kept at just over 50% utilization. On checking I found that the drive space had been filled with upwards of 240 files occupying 23.8 Gb, the names of which all started with the letters "pgbleach" (the remainder of each name was in the form ".n", ".nn", or "n.n--n", where n--n was a number string ranging in length from 1 to over 150 numeric digits).
I am assuming from the circumstances and the names allocated to the files that they were a byproduct of the "bleach free space" process. If this is the case:
1. Why would the files have been left cluttering up my C: drive?
I have run free space bleaches before without anything similar occurring.
2. What should I do to avoid a recurrence?
Do I need to limit bleaching to one drive at a time?
3. If it does happen again, what is the correct way to recover the disk space?
In this case I simply moved the files concerned to another drive so that they would still be available in case they proved vital. Nothing bad seems to have happened as a result, but I would like an assurance that it would be safe to delete them.
07-09-2012 01:43 PM
The way it "bleaches" the free space is by writing those files full of random data until the drive is full, then it's supposed to delete them. However I thought those files were each about 1Gb in size.
Usually they only get left behind if the user stops the process before it's done or closes the program before it can clean up those files. I'm not positive but I think if you ran it again and it finished properly it would have cleaned up all the leftover files.
I'm sure the program recognizes them by the name.
I can't answer your other questions, I think you may need to try it again and see if it works or the files get left behind again.
07-10-2012 12:50 PM
Thanks Dave, that seems to describe pretty much what happened. Most of the space was occupied by a series of files 1Gb in size, then there was a series of files with descending sizes (100 / 10 / 1 Mb, 100 / 64 Kb) presumably used to fill up the spaces remaining over and above multiples of 1 Gb.. There were also a lot of empty files so it does look as if the process was somehow interrupted before it was finished. I did notice that when I ran the bleach on another drive it stopped just before the end with a system message saying that the drive was almost full -- maybe something similar happened with the C:\ drive.
As a final check, I will run another bleach on the C:\ drive and watch what happens in detail.
07-10-2012 01:16 PM
I don't overwrite free space anymore, I used to do it a lot until I realized how difficult it really is to remove sensitive or personal files from a hard drive. Even with a good "bleach" it's difficult to do from "inside" windows because certain folders and locations are in use by windows and can't be overwritten.
I used to have a hard time overwritting free space even in "my documents" folder and it seems to me that would be the most natural place for people to keep things.
It got to the point where I would first reboot so less things would be in use by windows, then I would bleach the free space, reboot, defrag the system and bleach again. Then I would run a data recovery program and still see things that were not removed.
You will have to try it yourself.
But if you happen to be a doctor, lawyer, or handle peoples personal information or credit card data, do not rely on any tool that runs inside windows to overwrite the free space.
You need an encrypted partition or container to hold that stuff and you need to wipe the free space from "outside" of windows using a dual boot or bootable CD.
Bleaching free space is only good for hiding "embarassing" stuff from non-computer experts.
And yes, when you run it on XP, right before it finishes windows pops up a warning about low disk space. When that happens I don't think you want to do anything, let the program finish on it's own. Also be aware that XP usually will delete all the system restore points in a low space situation in order to try to keep windows running.
07-12-2012 12:23 AM
Regardless of the actual value of the process there does seem to be a problem with the implementation .
I tried the bleach on drive C:\ again. It worked quite smoothly at first, creating twenty-three 1 Gb. files, and then working its way down through 100 Mb., 10 Mb., etc. files. It was when the file sizes concerned got down below the 1 Mb. level that thing started to look a bit peculiar -- heavy CPU usage, multiple "Low disk space" messages, generation of chains of files with names of ever increasing length most of which were empty (0Kb.).
Since it had taken about half an hour to bleach the first 23 Gb. of 23.8 Gb. of free space, I reckoned it could not take longer that a further quarter of an hour at the outside to complete the process. Instead, one hour later I was still sat at the PC watching extra files get generated, and the "Bleaching free disk space ..." count on the NU "Clean your Disks" display bobble up and down over a few hundred Kb.
At this point I left the process to get on by itself for an hour or two. When I returned the good news was that Norton Utilities was no longer running, the bad news was that the C;\ drive was practically full of "pgbleach... " files. To add to the problem, when I tried to delete these myself the system reported for some of them that I would need a later version of Windows to do so.
I consider this behaviour to be an error. NU should either clean up the files or failing this issue an error message. Alternatively it is running some exception condition that it can't handle. Is there any way that I can escalate this?