I quite often get older computers donated either for recycling, passing on to less fortunate or simply for the scrap yard.
Before these leave me for another life or home I try hard to erase all posibilities of data theft or discovery of images, documents etc. I dont believe there is anything unsuitable on them but links to bank, credit cards, or personal details I want to make sure its not possible.
Many years ago with dos or windows, you formatted the disk, but in truth it did not do much just killed the FAT so you could get somethings back. Recovera from pirifom was excellent.
Now it tends to be older windows boxes I get, so I do a format to Linux format using the disk program, in mint 2 options rapid (5 mins) or deep couple of hours, all depends on size of disk.
I also convert it to linux ext4 format not FAT.
I will then install a clean new copy of mint.
Do you consider that secure ?
Do you do different ?
Apple have several pages on the site on how to clean a mac before resale.
I know answer, take disk out and distroy physically, I know societies exist for data recoveryâŚ
replace âsdxâ with your own disk name
Dont get the name wrong or you may erase your own computers disk.
It does not matter how the disk was formatted, âddâ overwrites everything, even the MBR
Used to be part of my job - data wiping hard drives from decommissioned Sun Solaris servers.
The Solaris âformatâ (not dissimilar to Linux fdisk) menu system, available when booting off a Solaris ISO - offered several choices - one was four passes of writing 0âs and 1âs - that was considered as satisfactory by the US militaryâŚ
So - I guess - in Linux would could just - several times, use dd to dump /dev/random onto the physical media - over several (e.g. 4) passesâŚ
Me - Iâve never done it for my personal stuffâŚ
Wow powerful command !
Just as an aside to that when linux formats the disk it marks bad sectors to not be used, If you use the write zero what does it do with bad sectors ?
I think today the disk controller looks after bad sectors, regardless of how or what you
write to the disk.
That was not always the case. You used to do it by hand .
powerful command
Not called âdata destroyerâ without reason.
BTW dd is one of the oldest Unix commands. It was one of the few Unix commands stolen from earlier systems⌠hence its strange non-standard syntax
In case of ssd drives, I would ask the firmware to do it. Doing it manually via de os (for example sending an infinite amount of zeroes marching to that disk) may actually harm the disk
The erase methods given in that article tell the SSD to flag each block as erased.
They do not erase every byte, they set set every block up as available for writing.
I imagine someone could still read the block contents?
Sorry for the question, but just so I understand: isnât constantly sending â0â or a full copy of an SSD that is completely full to another SSD the same thing? Isnât it all data?
isnât constantly sending â0â or a full copy of an SSD that is completely full to another SSD the same thing? Isnât it all data?
I have been asking myself the same question.
Yet, one can read numerous articles which say dont erase an SSD by writing zeros
It does not make sense.
Surely an SSD can endure one complete write without seriously degrading its expected lifetime?
Neville
Hi Neville,
For me, as a layman, SSD memories are non-volatile memories (flash memories) and, from my point of view, there are only two ways to test the memories (Iâm talking about the integrated circuits, or âchipsâ as some people call them) and the factory date retention: set the data of the memories to zero, analyze, set the data to 1 and analyze again or use a pattern between 0 and 1, but the memory has to be written and read and analyzed.
There is a problem with limiting writes to memory. Iâve read articles, but I havenât been able to find the technical reason for this.
I understand writing to ssd wears them out quicker than normal hard disks, but not sure. Hence I dont use them prefer read physical disks. But know my phone tablet are ssd.
I am no expert, but from my reading, any SSD the size of 240 GB or larger will probably last at least 5 years and maybe more for a home user. Today a disk of 240 GB is consider a small disk.
There was a lot of hype (some justified) about SSD wearing out when they first came out. But these early SSD where 60 GB or a lot smaller. Fewer cells meant the cell were being used more often.
To make a SSD last longer, I read that leaving about 25 to 30% of the disk space free. This allow âwear levelingâ to be used.
I visited an SSD manufacture of a 240 GB SSD. Their guarantee was â3 years or 100 TBW, whichever comes first.â So if a home use wrote 50 GB a day to this SSD?
1 TB = 1000 GB â 100 TB x 1000 = 100,000 â 100,000 / 50 GB per day = 2000 days
2000 days equal about 5 1/2 years. I believe for a home user writing 50 GB per day seems high.
Is my math correct?
Well, from what I read there was no way any data could be recover. One person said âSecure Erase (in most instances) doesnât tell the SSD to write anything, it literally just tells the SSDs âopen all the gates and let the voltage dump out to groundâ. Which generally makes it much faster then attempting to re-write.â
I am assuming he means that all the cells with â0â would stay that way and all the cells with â1â would now be â0â. With all cell setting at â0â that would mean no data and nothing to recover.
I could be wrong and it would not be the first time.
I still donât understand why not writing all â1â or â0â to a SSD would not format it properly. In my earlier example about SSD usage, writing 240 GB of data to a 240 GB disk would only account for 5 days usages out of 2000 days.