![]() You simply can't use cells that are already in use or marked as bad. It is never the wear levelling algorithm that decides where things go. It has to know which cells are already used, which cells are marked as bad and it has to go through things like the wear levelling algorithm. The controller on the ssd decides where the data will be written. So why doesn't OS X and Linux defrag SSDs?ĭon't just reply to a post, read it first! I've already explained it numerous times why it has nothing to do with it. Again, if you saw that on an HDD, you would say it needs a defrag so the head will not need to spin as much. The data sure looks scattered around to me. Because it needs to move to get data, and that is a performance hit. If a HDD has data scattered around the drive to hell, you would say it needs to be defragged. ![]() In an SSD data cannot be SCATTERED around the drive? By that definition, you can have empty cells that WERE used before in between cells that ARE being used. It was my understanding that it makes sure each cell gets equal use. So all data on the SSD is always next to adjacent cells? There are no empty cells AT ALL between data? If I have a 512GB SSD and only use 100GB of it (deleting and adding stuff conatantly), I am NEVER touching the other cells? If so, then yes, I do not know what wear leveling does. Do not just say: "obsessed with X much?". If it does not relate to the issue, EXPLAIN it. Um, it does not matter if I mention it numerous times. Very nice read and illustrative pictures. They'll show you exactly how files are stored on an ssd. Talking about having a "nice attitude".Īnandtech has some old but relevant articles about how an ssd works. You start flaming an article with complete misinformation. Yet you keep going on about wear levelling as if your life depends on it. Bringing up carrots would be the same thing. It is definitely not part of that discussion because, again, it has absolutely nothing to do with it. Same here since every ssd out there has garbage collection by default which works about as good as TRIM does. Only those that are available (some are dead like bad sectors, some are already in use, some have already had a lot of writes, etc.). In case of an ssd there could very well be different levels of fragmentation (at filesystem level which is what is being discussed in the article but also at NAND cell level) but one should definitely not mix them up. What defragmentation does is grouping those pieces of files together and also fill those pages/sectors as efficiently as possible. Fragmentation means that parts of files are everywhere and pages/sectors aren't filled up efficiently. The ssd might have NAND cells but there is much more to it than just that. Those cells can't be written and thus not all cells will be written to equally. ![]() It can't be because you also have data on the drive that just stays there. What wear levelling does is make sure that cells are written to equally but it isn't very strict. There is nothing correct about your description of wear levelling! You really need to research what wear levelling is because the above shows that you have absolutely no idea what it is at all. This fixes a couple of problems like not having enough inodes and a slowdown of disk speed (read and write). Defragmentation is all about grouping files. Wear levelling on an ssd is done via an algorithm at write time to make sure that each cell gets an equal amount of writes. A fragmented filesystem causes all sorts of problems.īecause you mention it just about everywhere no matter if it makes sense or has anything to do with it or not. It's just not the only reason why you'd do a defrag and that is what the article is trying to explain. Normally you'd do that to increase performance due to the way a hdd works. The only thing that is different is the reason for doing the defragmentation. Defragmentation is done on the hardware layer thus the drive, not the filesystem. It only tells the ssd to clear certain NAND cells which is completely different than a defrag where data is moved around so it is not all over the place but neatly ordered on the drive (both ssd and hdd). TRIM has nothing to do with defragmentation whatsoever.
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