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引用:

Originally posted by chaotommy
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

我個人覺得第一個人說的可以參考的地方
1. 如果INTEL可以以 3.0Ghz 的CPU來賣
他絕對不會以2.4 Ghz 來賣給客人的
為何INTEL會以 2.4Ghz 來賣給客人呢
因為這個CPU沒有通過3.0Ghz的品質管理
而只有通過2.4Ghz的品質管理

2. 之所以賣成120GB 而不是 250GB
是因為其它超過120GB的空間是不符合250GB的品質管理
也就是說硬碟公司有測試過
然後那些多餘的空間是有問題/不穩定的空間
所以才沒釋放出來

我個人覺得第二個人說的可以參考的地方
1. 如果硬碟公司可以賣為160GB的硬碟
他們絕對不會以80GB的容量/價錢來賣給客人的
可以多賺點錢為何不呢?
2. 把容量給變大了(比如兩倍)
是覆蓋了其它的地方
比如A覆蓋B
或B覆蓋A

不好意思
翻譯的不好
但意思到了就好~

LINK:

http://www.theinquirer.net/?article=14608

還有其它兩段文章
但是 jason040 兄上面已經解釋很清楚了...(原理)
懶的翻譯了
說的都是為何NORTON GHOST會有這樣的現像發生
....
技術文章
自己看吧...

這樣得邏輯是說得通的....
我也贊同這樣的說法...畢竟天下沒有這麼好康的事.............