SSD & Linux

[oldman]

Možda malo pomogne
https://forums.linuxmint.com/viewtopic.php?t=163939

EDIT by Vl@do: nije ti radio link dok nisam dodao dvotočku iza "https".

[shrike]

Možda malo pomogne
https://forums.linuxmint.com/viewtopic.php?t=163939

EDIT by Vl@do: nije ti radio link dok nisam dodao dvotočku iza "https".

Iz vezanog članka:

TRIM is important for this sole reason: the more LBA entries (or LBA ranges) the FTL map contains, generally speaking, the worse the SSD performs.

Without TRIM, the SSD’s FTL map, over time, will lack any indication of available LBA ranges. This in turn forces garbage collection (a.k.a. GC) to be used instead, which is significantly less efficient than the OS (or application) telling the drive “I’m done with these LBAs”. GC has the major downside of halting all I/O to the drive while its internal calculations/analysis are performed (else risk marking an LBA or LBA region as unused at the same time as the filesystem/OS requesting use of that LBA for a legitimate file). The GC implementation and its behaviour varies between drive models and drive vendors, including some vendors going as far as performing actual filesystem-level analysis on the drive itself (something I feel is extremely risky).

Ukratko, ukoliko ne radite TRIM ili nemate discard , prije ili kasnije će se zapuniti FTL mapa na SSD-u koja govori koji prostor je slobodan, tada će se pokrenuti GC (garbage collector tj. kolektor smeća) koji je bitno neefikasniji te zaustavlja sve diskovne operacije dok ne završi.

[oldman]

@ Vlado, hvala !

[bertone]

Kako je meni lijepo... ja ništa ne osjetim

Da provrtiš fstrim bi osjetio Iako, možda ti distra ima cron neki koji to vrti automatski pa misliš da ti ne treba.

Mislim da se od početka ne razumijemo ... tu i tamo (možda jednom mjesečno ili jednom u dva mjeseca) odradim fstrim ručno... moje je pitanje bilo zašto imate potrebu automatskog trima na dnevnoj ili tjednoj bazi i što dobijete time (jel' tolika muka napisati naredbu za trim i opaliti enter)

[shrike]

Kako je meni lijepo... ja ništa ne osjetim

Da provrtiš fstrim bi osjetio Iako, možda ti distra ima cron neki koji to vrti automatski pa misliš da ti ne treba.

Mislim da se od početka ne razumijemo ... tu i tamo (možda jednom mjesečno ili jednom u dva mjeseca) odradim fstrim ručno... moje je pitanje bilo zašto imate potrebu automatskog trima na dnevnoj ili tjednoj bazi i što dobijete time (jel' tolika muka napisati naredbu za trim i opaliti enter)

Ovisi što radiš, ali 1 u 1-2 mjeseca je prerijetko. Drugo, bitnije, sve takve stvari treba automatizirati i ostaviti što je manje moguće da ovisi o sjećanju i navikama.

[Bunker]

Kaj nema automatike ( bar u zvucnijim distrama ) pa da sa ssdom nemas dodatnih rucnih aktivnosti ?

[Bunker]

Ekipa, možete li mi preporučiti neki pouzdani način kako izvršiti secure erase na ssd disku i tako ga dovesti čim bliže tvorničkom stanju ?

Tražio sam ali nisam našao pouzdani način i najčešće naletim na nekaj ovakvog : Even if you use DBAN to shred the entire disk, you're only shredding the logical blocks. And the SSD spare area has more physical blocks. At some point currently assigned physical blocks will be swapped out to the spare area (with the current content of the block NOT shredded) and a new physical block will be moved from the spare area to currently assigned area.

Only the SSD's firmware secure erase command (if it is actually implemented) does actually securely erase a physical block. Everything else just wastes your time and doesn't actually erase anything, just reassigns a new physical block to that logical block you're trying to erase.

[shrike]

hah. Uključi hw enkripciju diska. napuni ga 100% sa /dev/urandom, zatim sa hdparmom secure eresaj.

[Bunker]

@shrike

Hvala, no zasad još gajim nadu da ću naći neki easy way ..

No obeshrabre me ovakvi tekstovi :
SSD flash memory cannot overwrite existing data in a classic manner. In an HDD system, the Operating System can request that new data be written to the same location where data is already stored, and the drive will directly overwrite the old data (magnetically). In an SSD, however, the target area must first be erased before it can be written to locations previously holding data. This is happening because of the internal structure. Flash memory is divided into blocks, sub-divided in pages. Data can be written directly into an empty page, but only whole blocks can be erased. So if you want to erase some of the data in a block, the rest of the data will be copied to another and the initial block will be erased or marked usable/empty.

The process is handled by FTL (flash translation layer) which has to do something like this when you change a very small amount of data: read one whole physical block (which let's say contains 64 pages - it can be up to 256), replace what you edited (let's say 4 pages) while keeping the rest intact (60 pages), erase a new block somewhere on the device and finally write the new set of 64 pages on that block.

TRIM support enables the old blocks to be considered empty, even if they have not been erased yet, which improves endurance.

The result of all that is that physically, some data still exists in marked-as-empty blocks and may be theoretically recovered by special means.

But this also simplifies a lot free space erase. You can just make a self-expanding file to occupy all space or copy any random data just to reach 0 free space and at that point all your previous blocks are practically irreversibly erased.

If you want to completely wipe the drive, you can use any tool supporting ATA Secure Erase, which electrically nullifies all data in the blocks. The tools are vendor specific (Corsair SSD Toolbox, OCZ Toolbox, Intel Solid State Toolbox, Samsung Magician Software). These essentially set all available blocks to the “erase” state (electrically), which is what TRIM uses for garbage collection purposes (and with which erases the blocks with before usage). The blocks remain empty with no information on their initial content.

So, to clean an SSD you just have to follow one rule: use all it's space for something. If a simple copy-a-big-file seems strange, you can always create an encrypted partition taking all the space, copy data there, then erase it and re-create it. But taking all the space with junk data is enough for a complete clean-up.

[shrike]

Pa moje upute ti rade što i taj tekst koji si citirao i zapravo je jednostavno, ali dd dio traje dugo. Prvo sa parted izbrišeš sve particije:
sudo parted /dev/sdX
rm 1
rm 2
rm 3
..
rm n
mklabel gpt
quit
#########
sudo dd if=/dev/urandom of=/dev/sdX

Znači nakon što sa parted izbrišeš sve particije i postaviš novigpt (sada više nema particija, samo disk), zapuniš čitavi disk sa random podatcima (urandom ti je na linuxu isto što i random, razlika je u blocking/nonblocking, ne i u kvaliteti)