Eraser and SSD performance

[sxr7171]

So I found a program called eraser. I'm sure it is one of many of its kind. It lets you "secure erase" the unused disk space of your drive. It even lets you choose which wiping methods you can use.

Eraser: http://www.heidi.ie/node/6

In the settings I can make it write "00000000" to each byte. So if I make it write that "00000000" pattern to all unused areas of my SSD, would it have the same effect of secure erasing an SSD but only for the portions of the drive that are not used?

I suspect that there is no free lunch in computing, but I am throwing this out there for people who know more about how an SSD works. If this works it would be a great tool to write zeros to the drive and use a program to consolidate free space hopefully returning the SSD to near factory performance.

 

[taltamir]

you know, if you had read any of the anantech articles about SSD you would know it...
Write 00000 is not the same as ERASING. It is erasing and then writing 0s.
Which is bad because SSD performance is poor because it can only delete 512kb at once (nothing smaller), and can write 4kb at once... so to write 4kb you need to read the 508kb on the same erase circuit, erase the entire 512kb, then write the 508kb of old data back to the exact same spot it occupied before unchanged (what a waste, eh?), and then write the 4kb to the now freed up 4kb spot.

An "eraser" can simply tell an SSD to ERASE everything without writing 0s to it. Which will give you a speed boost, until you fill the drive again.

The trim command will eventually help, by allowing it to erase erased data right away (read 508kb, erase 512kb, write back 508kb leaving 4kb erased and ready to be written to). Although at the cost of life (writes)

 

[jimhsu]

Additionally, SSDs are in an erased state with "1" bits, not "0" bits due to the way NOR and NAND are designed (programming is always 1 to 0). I discussed this in length in one of the posts on OCZ. The conclusion is that without a TRIM command, all you are doing is writing the respective bits on the drive; even though 1 is the erased state, the LBA that addresses that page believes that the page contains data (a string of 1's) -- therefore, the page is not available for writing.

Another explanation is that using whatever bit pattern with Eraser does not actually write that bit pattern on the drive. Remember that SSDs have smart wear-leveling; thus, the LBA view of the drive is diffferent from the actual physical layout of the drive.

See http://www.ocztechnologyforum....showthread.php?t=53470

 

[jimhsu]

PS The point of SECURE ERASE is to basically tell the SSD that all blocks are valid for writing by 1) clearing all entries in the LBA, and 2) resetting all locations to an erased state "1". Currently eraser cannot do this.

 

[sxr7171]

Couldn't there in theory be a program that in theory could write "1" bits to all unused areas of the drive while the OS is still on the drive? Would that help the situation?

 

[daw123]

If you read this article, then you will understand how SSDs work. btw the article is long, but very informative.

http://www.anandtech.com/stora...owdoc.aspx?i=3531&p=31

 

[taltamir]

Originally posted by: sxr7171
Couldn't there in theory be a program that in theory could write "1" bits to all unused areas of the drive while the OS is still on the drive? Would that help the situation?

its not write one, its remove the charge.

Heck MLC flash by definition can have a four possibilities in each cell as WELL as a "empty", so the "Write 1" is completely and utterly WRONG.

There are situations where the cell has no charge, if it was freshly erased,never written to, or if it failed. when that happens it will be registered as NO CHARGE rather than a 1...

And supposedly there is an intel program that can erase all cells on an SSD, should work with non intel drives as well.

http://www.anandtech.com/stora...howdoc.aspx?i=3531&p=5

this page shows a picture, it shows the 1s and 0s of flash, but when you ERASE it you completely remove all charge from the cell, meaning its neither 1 nor 0.

 

[usernamereserved]

When NAND is used in a MLC configuration it can store 2 bits of data.

00 the cell is full
01 the cell is partially full
10 the cell is partially empty
11 the cell is empty or contains no valid data

Writing zeros or ones to the drive will not erase the cells as has already been pointed out.
I know of only 3 ways to erase a cell.

1: Use a program such as HDDErase which does a secure erase and also wipes the LBA.
2: Use the command: secure erase from Unix/Linus
2: Flash the drive with a firmware which re-works the NAND anyway.