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How Intel and Micron May Finally Kill the Hard Disk Drive
itwbennett writes: For too long, it looked like SSD capacity would always lag well behind hard disk drives, which were pushing into the 6TB and 8TB territory while SSDs were primarily 256GB to 512GB. That seems to be ending. In September, Samsung announced a 3.2TB SSD drive. And during an investor webcast last week, Intel announced it will begin offering 3D NAND drives in the second half of next year as part of its joint flash venture with Micron. Meanwhile, hard drive technology has hit the wall in many ways. They can't really spin the drives faster than 7,200 RPM without increasing heat and the rate of failure. All hard drives have now is the capacity argument; speed is all gone. Oh, and price. We'll have to wait and see on that.
Well, the Samsung 3.2 TB drive claims that you can read/write the entire drive every day for five years before failure. It's my understanding that at one point, SSDs were notorious for gradually declining over time, but that today's generation of SSDs basically has reliability out the wazoo. I can't quote you stats on it, but anecdotally, I've had a couple of SSDs in my computer for several years now, I leave it on 24x7, and I've never had a problem.
...Yet. YMMV.
I don't know why Intel and Micron get any special consideration given that right in the summary the fact that Samsung has already announced the same move.
Also incorrect assertion that drives don't go faster than 7200 (there are 15k drives, just they are pointless for most with SSD caching strategies available).
XML is like violence. If it doesn't solve the problem, use more.
That's the thing. Most people who need 3.2 TB of space will only write to each location a few times, and data won't change very often. Sure, some writes will be happening, but not even close to the magnitude that you'd need to wear out one of these drives. There might be some cases in commercial applications where you'd need to write that every day, but the typical desktop or laptop is never going to see that kind of usage.
Anthropic principle: We see the universe the way it is because if it were different we would not be here to see it.
Most current MLC (multi-level cell) implementations can sustain anywhere between 1000 and 3000 write/erase cycles per cell. This is better than TLC (triple-level cell, max 1000), but far worse than SLC (single-level cell, max 100k up to a million, depending on the technology).
The problem is the way how flash itself works, and how smart your controller is. Unlike a disk, flash must be erased before writing. And here is where the problem comes: flash data is stored in a page of cells, with typically 8 pages of data per "block". Erasing happens on the block level. So in order to erase a single page of data, you need to erase all 8 pages in a block. Since you need to keep the data of the other 7, you first need to copy that data into another block, erase the original one, write all data back and erase your "tmp" block. The churn on blocks happens a lot faster than what you'd think.
Having that said, for consumer products, MLC or TLC is perfectly fine. For enterprise, not so much.
You'll see that in the price, obviously. TLC is the cheapest, followed by MLC, and the most expensive technology is SLC.
I'm not a complete idiot... Some parts are missing.
Well, the Samsung 3.2 TB drive claims that you can read/write the entire drive every day for five years before failure.
Such statistics are meaningless in my book. Light bulb manufacturers claim their bulbs will last five years or seven years but when you look at the fine print they say that's given under the idea you're turning the light on, leaving it running for 3 hours, and turning it off once per day -- nobody uses light bulbs like that.
Comparing a $10 USB stick with an SSD is like comparing turtles to cheetahs. Those USB sticks might write at 2-5 megs/sec. Maybe. 1/100 the speed of a good SSD. It's not a cromulent comparison.
That may well be, but have you ever looked at a turtle's drag coefficient?
When our name is on the back of your car, we're behind you all the way!
The problem is that once PC is turned on, there is not much use for the SSD speed.
Ever tried loading the next level in a game? SSDs make a big difference.
And, you've completely forgotten all the other uses (both enterprise and personal) like database, video editing, running VMs, etc.
That's actually what they do.
1) Select an empty block.
2) Copy the data into ram on the device
3) Write the new physical block
4) Update the virtual/physical block map
5) Mark the old block as empty
Under common usage patterns, you can expect up to 25 years life for first-gen SLC, 15 years for first-gen MLC, 10 years for current-gen MLC, 5 years for current-gen TLC. MTBF is lower due to defective cells and such, but that's also true for HDDs.
you first need to copy that data into another block, erase the original one, write all data back and erase your "tmp" block. The churn on blocks happens a lot faster than what you'd think.
If that's the case, then why are they not copying the data to ram contained on the drive itself? Seems like an awful waste of cycles with a relatively simple fix. Is it just a cost issue?
Any wear levelling worth its salt will not do what the grandparent wrote. You simply do not change one page in a block. If you write a single page, that is handled by mapping that page to another (free) block and maintaining a mapping table for which LBAs are currently stored in what blocks. However, if you are doing single-sector writes, or in turn repeated I/O flushes of the same sector, you still see a lot of write amplification. To keep data integrity, the mapping tables also need to be kept updated in a correct way (or at least uniquely recoverable by scanning through all blocks after a hard power off).
The actual wear leveling algorithms are proprietary, but rest assured that they do not use flash as temporary memory, and neither do they read an erase block, change one sector and write the erase block back. One thing flash controllers do is maintain a list of unused sectors. So, if you write to one sector, the data goes into an empty sector of a different erase block and the controller remembers that the sector's old location is now unused (and where the sector is now). That's where the TRIM command helps: It marks sectors as unused without using up a different sector somewhere else. When the drive needs more free erase blocks, it copies the remaining data from mostly "abandoned" erase blocks and flashes (erases) the old erase block. All that and more brings down the write amplification, which measures the average number of sectors actually written for each write to a sector. Intel claims a write amplification of just 1.1 for one of its controllers. Also, wear leveling makes sure that erase blocks are used evenly. Otherwise writing the same few sectors over and over again would burn out the drive in seconds. All in all you can expect to write at least a few hundred times the capacity of the drive, in any order and to any sectors you want, before you need to worry about flash cell wear.
No, it doesn't. It doesn't protect you against losing data in a fire, it doesn't protect you against losing data to malware, and it doesn't protect you against losing data to making a mistake. All changes are automatically propagated across all disks. Backup protects you against losing data.
What RAID 15 does is protects you against losing a day of work because one disk failed - that is, it protects against loss of uptime.
With 3 bits per cell, how long before the data fades?
This is the reliability issue that nobody wants to talk about. I am sure that many others are like myself, with a closet full of old PCs. I like the idea that if I were to pull one out and power it on after having sat unplugged for a span of years, it would still boot (CMOS battery BIOS issues not withstanding) and would still have all of the data I left it with.
SSDs on the other hand won't even guarantee that your data will still be there after *only one year* of being powered off, and as we've dipped below the 34nm process, sometimes SSDs are warranted for even less.
http://cylan.deviantart.com/gallery/
Risky Array of Imminent Disaster.