Slashdot Mirror
AnandTech Gives the Skinny On Recent SSD Offerings
omnilynx writes "With capacity on the rise and prices falling, solid state drives are finally starting to compete with traditional hard drives. However, there are still several issues to take into account when moving to an SSD, not to mention choosing between a widening array of offerings. Anand Lal Shimpi of AnandTech does a better job than anyone could expect detailing those issues (especially those related to performance) and reviewing the new offerings in the SSD arena. Intel's X25 series comes out on top for sheer speed, but OCZ makes a surprise turnaround with its Vertex drive giving perhaps the best value."
This may be the most informative and practical article I have read in a long, long time. It's definitely going to influence my SSD hardware purchases for the foreseeable future.
Reformatting isn't sufficient to get back to new performance, you have to issue an ATA SECURE ERASE command.
And you can't run a filesystem built specifically for flash on these drives, with Linux or otherwise, because they don't present a flash interface. They present an SATA interface.
In any case, the take-home message is probably to consider the drive's "used" performance as its real performance. If the drive is not a crummy one (watch out for those), it's still _much_ faster than an HDD, and very worthwhile depending on your application.
No. Not use, but slower the more you write to it. You can read all the time and it doesn't speeds.
Not quite. Once it runs out of completely free blocks, the drives 'hit a wall', and from that point on they are significantly slower to write to.
But it doesn't continue getting slower and slower and slower and slower over time. Just that, at some point, it suddenly becomes x% slower to write to and stays that way.
The author does conclude even at the slowest possible speed the Intel model (he said he did a simulation where by writing to all the blocks at least once) that its still beats HDD.
The intel model is the fastest by far. The Samsung drives are also good. And the OCZ Vector was also good. (Not as good as the intel one, but still 48% faster than the WD veliciraptors, which is seriously still excellent.)
The important point however, is that the units that 'still beats HDD' doesn't mean "a little bit faster". They mean continue to royally spank an HDDs ass.
However, the other models, by comparison, are basically unusable.
Apparently it depends on the controller version which affects the speed. Intel put a good one in and the other brands no so good.
Its FAR more complicated than that by far. And the article is 30+ pages long for a reason. (30+ real pages, not bullshit 'half-paragraph per page' pages.
He said its still noticeable though sometimes.
In the sense that yes, once your drive 'hits the wall' the slow down can be noticeable relative to when it was new... but its still twice as fast to 5x as fast as the fastest alternatives.
There is also stuff the OS can do to mitigate the problem, once we have SSD aware OSes.
Essentially, the reason it slows down, is that once your drive has used all the blocks, it has to erase a block before it can use it again, and this can require it to read multiple pages in, erase the block, and write it back out again, which can take up to half a second.
The better controllers, including extra blocks that aren't reported to the OS, and adding OS awareness to the issue can essentially let the drive stay ahead of the random write requests, and erase blocks before they are needed, to ensure their is always a pool of completely erased and ready to go blocks available, and therefore keep the drive much closer to its 'like new speed' indefinitely.
"some geek"?
Anand has been around, reviewing hardware, for close to 10 years now. He is, rightfully so, considered an expert in hardware usage, performance tuning and over systems construction.
There are others out there with similar cachet.
He is far, FAR from just being "some geek".
It isn't. The whole point of TRIM is to erase a block before you're waiting to write something to it, ie. before your disk is full and you need to reuse the space. The garbage collection on a TI calculator is really defragmentation, to eliminate gaps between files. This is necessary because the calculators have the flash attached to the address bus, rather than behind a hard drive controller, and there's no MMU to give programmers a linear address space if there flash apps were to be discontiguous in memory. Thus, in order to load an app in to the calculator flash, there must be a contiguous region of available flash.
If you took 5 sec. to search his credentials you'll find he graduated from N. Carolina State with a CE degree.
His site has been in existence for quite some time and I find his articles are among the better ones on the net, but you may want to read others and compare. The reason why I like his articles over others is the depth of his articles. He describes the underlying architecture and provides thoughts on why he thinks a company chose a path with followups that either reinforce or refute a theories.
Mod parent up. I'm not arguing with him, but merely emphasizing a key point.
... and adding OS awareness to the issue can essentially let the drive stay ahead of the random write requests, and erase blocks before they are needed, to ensure their is always a pool of completely erased and ready to go blocks available, and therefore keep the drive much closer to its 'like new speed' indefinitely.
Actually, this is the part about the new sata Trim command. And ironically a part where Anand swings and misses completely, or it's dumbed down to a level where it is completely misleading.
It's not so much about making the OS SSD aware in the sense that the OS now knows about the inner workings of the SSD, but making the SSD aware of what space is actually used for data, and what has been discarded. Knowing what data blocks has been discarded means you can consolidate discarded blocks, by moving valid data to other pages, and then erase the page full of discarded blocks, so it is ready for writing new data.
So not only do you get write performance that doesn't degrade with time, but you can also store slightly more, because you don't have to reserve as much space.