*www.theinquirer.net/?article=14608[/url]]
Unused space on hard drives recovered
Regarding article "Unused space on hard drives recovered?" at this URL.
I am the "Linux SATA guy".
First, users are usually amused to learn that the capacity of modern hard drives is _unknown_, until it goes through the factory's qualification tests. The 120GB hard drive you purchased may have been physically identical to a 250GB hard drive, but simply it only passed qualification at 120GB.
Intel does the same thing with processors. A 3.0Ghz processor may be sold as 2.4Ghz, simply because it didn't pass qualification at 3.0Ghz but did at a lower clock speed.
Second, in the ATA standard there is a feature known as the "host protected area". This area is accessible from any OS -- but it requires special ATA commands in order to make this area available to the OS.
Third, all hard drives reserve a certain amount of free space to use for reallocation of bad sectors. These "spare sectors" are free space on your drive... completely unused until your hard drive starts finding problems on the physical media.
So this is old news
Although the host-protected area (HPA) can be used for insidious purposes such as DRM/CPRM that is completely hidden from the users, most of the "invisible free space" exists for a purpose -- either it's spare sectors for bad sector remapping, or its capacity that didn't pass factory qualification, that you don't want to use anyway.
Feel free to edit/reproduce/publish this email.
Jeff Garzik
Not speaking for my employer, speaking as an Open Source guy
Hi Mike,
About the "recover unused space on your drive" article:
Working for a data-recovery company I know a thing or two about harddisks....
One is that if the vendors would be able to double the capacity for just about nothing, they would.
All this probably does is to create an invailid partition table which ends up having:
|...new partition.............................
|old partition.................................|
overlapping partitions. So writing either partition will corrupt the other. It probably so happens that whatever situation people tried it, it just so happened that the (quick) format of the "new" partition didn't corrupt the other partition to make it unbootable.
And the 200G -> 510Gb "upgrade" probably has ended up with three overlapping partitions....
Roger
Commenting on an article you posted today about hidden hard drive space. It was brought to my attention from a link to it from HardOCP.
What is happening is that Norton Ghost creates a virtual partition on the drive, and the data for that virtual partition resides on one of the existing partitions. So as more data is added on the virtual partition, a file on the normal drive partition expands as well.
It's kind of like a disk image which is being mounted to a drive letter. All the data for it is still on the primary partition.
Hopefully that's clear enough to explain what is happening here. The extra virtual partition basically is defined as the amount of freespace on the partition to which the that virtual partition file actually resides.
In short: No miracle space here, don't bother the hard drives manufactures. Just using a feature in ghost in a weird way, but with no real benifits other than being able to boot a disk image without reszing all the partitions on your drive.
Peace
Matt
Hello.
Here's my take on this phenomenon as an IT professional. I have HAD THIS HAPPEN BEFORE, with Microsoft FDisk. Microsoft tends to recycle [crappy] code, and it would appear that the tools called by the Disk Management MMC snapin are no exception. I didn't immediately realize what had happened some years ago (I think about 4 years ago now), but FDisk's faulty start/end sector calculation code ended up causing the program to create a ~3GB partition after an existing ~10.8GB partition on a ~11GB drive, after I had used it to delete a ~200MB Linux partition. This resulted in ~5GB of corrupted data on the primary partition due to the fact that I was probably half asleep at the time and wrote things to the other partition. I was not impressed. Regardless, this is almost certainly what's going on. I'd suggest to anyone trying this to fill the first partition with one HUGE file, take an MD5 checksum, write something to the second one, repeat MD5sum, and compare.
Just my three cents...
Paul Nienaber
Hi,
I'm writing regarding the "unused space on hard drives recovered?" article at *www.theinquirer.net/?article=14597. As a frequent user of Ghost, both for work and personal machines, it is quite obvious all this method is doing is corrupting the discs' partition tables.
I'd be curious to know if the person who sent you this ever tried to FILL all partitions of the disc and then verify the data is usable. Basically, you're corrupting the hard drive's information that says its size and telling the computer it's larger-- it will definitely APPEAR that you mysteriously have tons of new space, but it WILL cause corruption and data loss.
I think at the very least you should put even more caveats on that story, before some punter comes by and wipes out all his important data by copying it to his new super-huge-hard drive.
There IS "lost space" on modern hard drives-- they do major amounts of error correction, data redundancies, etc. However, you're not talking anywhere near 50% of space lost. And even if you were-- is losing all error control worth a bit of extra space when you can pick up another 120GB drive for under $80US??
Justin Scott
