Long-Term Performance Analysis of Intel SSDs 95
Vigile writes "When the Intel X25-M series of solid state drives hit the market last year, there was little debate that they were easily the best performing MLC (multi-level cell) offerings to date. The one area in which they blew away the competition was with write speeds — initial reviews showed consistent 80MB/s results. However, a new article over at PC Perspective that looks at Intel X25-M performance over a period of time shows that write speeds are dramatically reduced from everyday usage patterns. Average write speeds are shown to drop to half (40MB/s) or less in the worst cases, though the author does describe ways that users can recover some of the original drive speed using standard HDD testing tools."
Reader MojoKid contributes related SSD news that researchers from the University of Tokyo have developed a new power supply system which will significantly reduce power consumption for NAND Flash memory.
TL:DR (Score:4, Insightful)
That article is a multi-page annoyance, the grammar is bad and we already have flash-aware filesystems like jffs2.
Re:Damn (Score:5, Insightful)
Re:File system? (Score:3, Insightful)
One of the biggest challenges of the coming years will be finding and developing filesystems (logical data stores) that take advantage of the strengths of flash memory while deminishing the weaknesses of it.
Our approach today is mapping large banks of Flash to look like a hard drive, and then using a filesystem that is optimized to reduce seek activity. (Cyl/Hds/Tracks-per-Sector..)
EXT3 on SSD, FAT on huge SD cards, it's just shoe-horning our old filesystems onto new media. It makes about as much sense as using a hard drive to store a single TAR image only.
Once we make the huge step of designing high-performance filesystems that are exclusively *for* flash media, then we can take advantage of some of the huge benefits that are distinctly flash.
Key things like journalling should be designed with the flash organization in mind: pages and blocks vs "sectors". That kind of thing.
Re:There's got to be some writable space here... (Score:5, Insightful)
That's so oversimplified as to be completely wrong.
The number of write/erase cycles on NAND is significantly less than a hard drive. Typical devices are rated for 10,000 cycles. Bleeding-edge MLC parts can be as low as 5,000 or 7,000 erase cycles.
But.. a well-designed device will perform accurate wear-levelling across all the available blocks, so it doesn't matter what kind of access the user performs -- the whole device will wear evenly.
There are indeed reserve blocks to mitigate premature death of some parts.
But, the most important part is the ECC mechanism. The parts don't just wear out and die, they get an increasing bit error rate. By overdesigning the ECC logic, you can squeeze longer life out of the parts.
It does not play guess and check.. well-recognized error correction algorithms like Reed-Solomon or BCH are used with really high detect/correct rates.
Once you have accurate wear levelling, excellent ECC, and some manner of failure prediction, then it doesn't make so much sense to keep all your flash "in reserve" ready to swap out other parts wholesale. You might as well involve all the parts in the mix, so you get longer wear throughout.
Re:TL:DR (Score:3, Insightful)
Flash-aware filesystem currently only works on embeded setup where there is direct access to the Flash.
Given the need for compatibility, SSD will always have a controller showing the SSD as a disk, but I agree that it'd be nice if they would add additionnal lower level access in the case the computer is able to use Flash-aware filesystem.
Re:SLC vs MLC (Score:5, Insightful)
To me, MLC has a conceptual problem of going against the fine tradition of binary computing, which is all about data integrity. Why don't we go back to analog computers for even higher densities, while we're at it.
Says someone that obviously has never seen the raw output of a HDD read head, or the optical laser in a DVD reader. The real world was always very ugly and analog, there's a helluva lot going on to give you a 0 or 1 answer.