Do solid-state drives get fragmented? And if they do, does it cause their performance to suffer?
Solid-state drives DO NOT require defragmentation. It may decrease the lifespan of the drive. Wear leveling technology purposely "fragments" the data to ensure the consistent life of the drive.
“Suffer”? No. Experience? Yes.
Fragmentation is simply when files are written to non-contiguous blocks. This is not a problem with a fresh, clean drive, but after a while, as the drive fills up and files are deleted, new files eventually begin to get written into whatever blocks are available which may not always be big enough for the whole file. There’s really no way around it (short of writing everything once to an empty drive then not writing anything ever again), not even with a better file-system.
However, as sblair pointed out, it’s not actually a problem with SSDs like it is with HDs because there is no head to physically move around the disk to collect data, so there is no performance penalty.
Also, as Marcin and Molly explained, SSDs need to scatter data throughout the whole drive to prevent the beginning of it from getting worn out while the rest of it remains unused. As a result, SSDs purposely fragment data to spread it around the whole drive. Also, you don’t want to defragment SDDs because not only does it defeat the purpose of spreading the data around, but all the extra writes wear it out faster. Robers gave a good explanation about how SSDs are different from traditional spinning disks and that the sectors on an SSD do not reflect the physical layout.
This is yet another benefit of SSDs over spinning HDs: fragmentation is no longer an issue.
SSDs : 5 (less power, less heat, faster, no fragmentation, smaller) HDs : 1 (longer lasting)
All this does not however mean that SSDs are the ideal, care-free storage solution. Aside from the fact that they wear out, there is a critical issue to be aware of. While it’s true that SSDs employ wear-leveling and their firmware manages sector mapping, that does not negate the fact that SSDs, like all storage devices that allow modification, do become fragmented which is death when you need to recover lost files.
Using a more tolerant filesystem like NTFS instead of FAT32 helps to some degree, but the fact is that a fragmented file is much harder to recover (if not flat out impossible) than one that is not fragmented. Of course in this case, “fragmented” means from the OS’ point of view irrespective of the physical layout.
The general consensus is that they can fragment, but that it's not necessary to defragment and, worse, it could lead to a shorter drive life. I like Tom's Hardware and their explanation when investigating Diskeeper's SSD defragmentation product.
You actually can suffer reduced performance from fragmentation on SSD. Fragmentation remains a logical problem because the OS/filesystem has to keep track of all the pieces of files, and the pieces of free space. As files shrink and grow and as free space becomes more logically fragmented, over time, I/O operations will naturally become smaller, while the OS/filesystem will naturally consume more CPU overhead to figure out where to put the next piece of data to store, or when reading more overhead to figure out where all the bits of a massive file are.
Basically, IOPS will rise as fragmentation grows. More IOPS generally is bad. Am I wrong?
This may not seem as evident with non-file-based systems like databases that store all their content in a massive blob of disk space (letting the DB manage fragmentation a layer or two up from the filesystem).
However, you can and will suffer from fragmentation even on SSD if you don't do something on some basis to mitigate the long-term effects.
SSD is really freakin amazing, but is not the panacea. Anyone who insists fragmentation is a thing of the past on SSD is most likely selling something.
The reason you suffer from fragmentation, generally, is because the drive head has to move to many different places to access the file. It has to physically move, which takes time. With a solid-state drive (SSD), you'll still experience the fragmentation, but there are no moving parts that have to actually move to the location of the other parts of the file, so you don't encounter the same symptoms (reduced performance).
Also, solid-state drives have a finite number of times that they can be written to. So, defragmenting them may actually reduce the lifespan of the disk while not really giving you the benefit of increased performance like you would experience with a disk that has platters.