SSDs do not, I repeat, do NOT work at the filesystem level!
There is no 1:1 correlation between how the filesystem sees things and how the SSD sees things.
Feel free to partition the SSD any way you want (assuming each partition is correctly aligned, and a modern OS will handle all this for you); it will NOT hurt anything, it will NOT adversely affect the access times or anything else, and don't worry about doing a ton of writes to the SSD either. They have them so you can write 50 GB of data a day, and it will last 10 years.
Responding to Robin Hood's answer,
Wear leveling won't have as much free space to play with, because write operations will be spread across a smaller space, so you "could", but not necessarily will wear out that part of the drive faster than you would if the whole drive was a single partition unless you will be performing equivalent wear on the additional partitions (e.g., a dual boot).
That is totally wrong.
It is impossible to wear out a partition because you read/write to only that partition. This is NOT even remotely how SSDs work.
An SSD works at a much lower level access than what the filesystem sees;
an SSD works with blocks and pages.
In this case, what actually happens is, even if you are writing a ton of data in a specific partition, the filesystem is constrained by the partition, BUT, the SSD is not.
The more writes the SSD gets, the more blocks/pages the SSD will be swapping out in order to do wear leveling. It couldn't care less how the filesystem sees things!
That means, at one time, the data might reside in a specific page on the SSD, but, another time, it can and will be different. The SSD will keep track of where the data gets shuffled off to, and the filesystem will have no clue where on the SSD the data actually are.
To make this even easier: say you write a file on partition 1. The OS tells the filesystem about the storage needs, and the filesystem allocates the "sectors", and then tells the SSD it needs X amount of space. The filesystem sees the file at a Logical Block Address (LBA) of 123 (for example). The SSD makes a note that LBA 123 is using block/page #500 (for example). So, every time the OS needs this specific file, the SSD will have a pointer to the exact page it is using.
Now, if we keep writing to the SSD, wear leveling kicks in, and says block/page #500, we can better optimize you at block/page #2300. Now, when the OS requests that same file, and the filesystem asks for LBA 123 again, THIS time, the SSD will return block/page #2300, and NOT #500.
Like hard drives nand-flash S.S.D's are sequential access so any data you write/read from the additional partitions will be farther away than it "might" have been if it were written in a single partition, because people usually leave free space in their partitions. This will increase access times for the data that is stored on the additional partitions.
No, this is again wrong!
Robin Hood is thinking things out in terms of the filesystem, instead of thinking like how exactly a SSD works.
Again, there is no way for the filesystem to know how the SSD stores the data.
There is no "farther away" here; that is only in the eyes of the filesystem, NOT the actual way a SSD stores information. It is possible for the SSD to have the data spread out in different NAND chips, and the user will not notice any increase in access times. Heck, due to the parallel nature of the NAND, it could even end up being faster than before, but we are talking nanoseconds here; blink and you missed it.
Less total space increases the likely hood of writing fragmented files, and while the performance impact is small keep in mind that it's generally considered a bad idea to defragement a nand-flash S.S.D. because it will wear down the drive. Of course depending on what filesystem you are using some result in extremely low amounts of fragmentation, because they are designed to write files as a whole whenever possible rather than dump it all over the place to create faster write speeds.
Nope, sorry; again this is wrong. The filesystem's view of files and the SSD's view of those same files are not even remotely close.
The filesystem might see the file as fragmented in the worst case possible, BUT, the SSD view of the same data is almost always optimized.
Thus, a defragmentation program would look at those LBAs and say, this file must really be fragmented!
But, since it has no clue as to the internals of the SSD, it is 100% wrong. THAT is the reason a defrag program will not work on SSDs, and yes, a defrag program also causes unnecessary writes, as was mentioned.
The article series Coding for SSDs is a good overview of
what is going on if you want to be more technical about how SSDs work.
For some more "light" reading on how FTL (Flash Translation Layer) actually works, I also suggest you read Critical Role of Firmware and Flash Translation Layers in Solid State Drive Design (PDF) from the Flash Memory Summit site.
They also have lots of other papers available, such as:
Another paper on how this works: Flash Memory Overview (PDF).
See the section "Writing Data" (pages 26-27).
If video is more your thing, see An efficient page-level FTL to optimize address translation in flash memory and related slides.
This question is very hard, especially in view of the fact that SSD technology
is in constant evolution, and especially since modern operating systems are
constantly improving their handling of SSD.
In addition, I'm not sure that your problem is with Wear leveling.
It should rather be with SSD optimizations designed to avoid block erases.
Let us first get our terms right :
- An SSD block or Erase block is the unit that the SSD can erase in one atomic operation, which can usually go up to 4MB bytes
(but 128KB or 256KB are more common).
An SSD cannot write to a block without erasing it first.
- An SSD page is the smallest atomic unit that the SSD software can track.
A block usually contains multiple pages, usually up to 4KB in size.
The SSD keeps a mapping per page of where the OS thinks it is located
on the disk (the SSD writes pages wherever it prefers although the OS will
think in terms of a sequential disk).
- A sector is the smallest element that the operating system thinks a hard disk
can write in one operation. The OS will also think in terms of disk cylinders
and tracks, even if they do not apply to SSD.
The OS will usually inform the SSD when a sector becomes free
(TRIM).
Smart SSD firmware will usually announce to the OS its page-size as the sector-size where possible.
It is clear that the SSD firmware would prefer always writing to empty blocks,
as they are already erased. Otherwise, to add a page to a block that contains
data will require the sequence of read-block/store-page/erase-block/write-block.
Too liberal application of the above will cause pages to be dispersed all over
the SSD and most blocks to become partially empty, so the SSD may soon run out
of empty blocks. To avoid that, the SSD will continuously do
Garbage collection in the background, consolidating partially-written
blocks and ensuring enough empty blocks are available.
This operation may look like this:
[![image1][1]](https://i.stack.imgur.com/wnOzX.png)
Garbage collection introduces another factor -
Write amplification
- meaning that one OS write to the SSD may need more than one physical write
on the SSD.
As an SSD block can only be erased and written a certain number of times before
it dies, Wear leveling
is designed to distribute block writes uniformly
across the SSD so no block is written much more than others.
The question of partition alignment
From the above, it looks like the mechanism that allows the SSD to map pages
to any physical location, keeping wherever the OS thinks they are stored,
voids the need for partition alignment. Since the page is not written where
the OS thinks it is written, there is no more any importance as to where the OS
thinks it writes the data.
However, this ignores the fact that the OS itself attempts to optimize
disk accesses. For classical hard disk it will attempt to minimize head
movements by allocating data accordingly on different tracks.
Clever SSD firmware should manipulate the fictional cylinder and tracks
information that it reports to the OS so that track-size will equal
block-size, and page-size will equal sector-size.
When the view the OS has of the SSD is in somewhat more in line with reality,
the optimizations done by the OS may avoid the need for the SSD to map pages
and avoid garbage collection, which will reduce Write amplification and
increase the lifetime of the SSD.
It should be noted that too much fragmentation of SSD (meaning too much
mapping of pages) increases the amount of work done by the SSD.
The 2009 article
Long-term performance analysis of Intel Mainstream SSDs
indicated that if the drive is abused for too long with a mixture of small and large writes, it can get into a state where the performance degredation is permanent, and that with Wear leveling this condition may extend to more
of the drive.
This condition is the reason while many SSD owners see performance degrade
over time.
My final advice is to align partitions to respect erase-blocks layout.
The OS will assume that a partition is well-aligned as regarding the disk,
and the decisions taken by it on the placement of files might be more
intelligently done. As always, individual idiosyncrasies of OS driver
versus SSD firmware may invalidate such concerns, but better to play it safe.
Best Answer
Currently, all IDE/SATA hard drives expose either 512B or 4KB sized blocks (depending on make and model) for read/write operations. Those are the only two options available (shame, because I can imagine other LBA sizes being very advantageous).
When an OS reads/writes to a hard drive, it has to manage the difference between the file system's sector size and the hard drive's LBA size. For a 512B hard drive, writing a 4K NTFS sector requires 8 x 512B writes. You can see how a 4K drive might perform better given that the same operation would only take 1 x 4K write.
The way SSDs do things internally varies by make and model. Page sizes can be different.