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Taking a Hard Look At SSD Write Endurance
New submitter jyujin writes "Ever wonder how long your SSD will last? It's funny how bad people are at estimating just how long '100,000 writes' are going to take when spread over a device that spans several thousand of those blocks over several gigabytes of memory. It obviously gets far worse with newer flash memory that is able to withstand a whopping million writes per cell. So yeah, let's crunch some numbers and fix that misconception. Spoiler: even at the maximum SATA 3.0 link speeds, you'd still find yourself waiting several months or even years for that SSD to start dying on you."
100000 writes? 1M writes?
What the fuck is this submitter smoking?
Newer NAND flash can sustain maybe 3000 writes per cell, and if it's TLC NAND, maybe 500 to 1000 writes.
100,000 is only for SLC NAND. MLC, what is currently in most SSDs, is only 3,000, and TLC (found in usb drives, samsung 840, and probably more SSDs soon because it's cheaper) is only 1,000.
Is 1,000 fine for most people, yes.. but you should be aware of it. I have a fileserver that writes 200gb per day.. which would kill a Samsung 840 in about 6-7 months.
http://www.anandtech.com/show/6459/samsung-ssd-840-testing-the-endurance-of-tlc-nand
Obviious Troll is Obvious but... while SSDs can & do fail (just like old hard drives can & do fail), the reason for SSD failure in the real world is very rarely due to flash memory wear. Hint: If your flash drive suddenly stops working one day, that ain't due to flash wear, which would manifest as gradual failure over time.
AntiFA: An abbreviation for Anti First Amendment.
Our company experienced what we believe was its first age-related failure in October of 2012, an office PC with an Intel SSD drive in the value oriented line of 2008 (which was still high at the time). Basically the drive behaved as a mechanical drive would behave with an occasional bad sector and we were able to successfully image the data to a new one. Out of 200 Intel drives, that's pretty good. (We did have one failure in 2010 but that was an outright dead drive and we were able to RMA it). Not sure if this contributes anything to the conversation but I figured I'd throw this out there.
The Intel X25's in my PC, from 2009, are still humming along nicely and my last benchmark produced the same results in 2012 as they did in 2010. But I've gone so far as to set environment variables for user temp files to a mechanical drive, internet temp files to a RAM drive and system temp files to a RAM drive, offsetting the wear leveling.
Had an SSD in my laptop for just over a year and a half now, no issues what so ever. Daily use as well.
+1 IDisagreeSoHeMustBeATrollOrAnAstroturferOrAShill
But if your SSD is nearly full with data that you never change, wouldn't all the writing happen in the small area that is left? This would significantly reduce lifetime.
I believe all the major brands actually move your data around periodically, which costs write cycles but is worth it to keep wear balanced.
"I zero-index my hamsters" - Willtor (147206)
meaningful life specs are tough to come by for flash. Yes, as noted above, SLC NAND has a rated life of 100k erases/page on the datasheet, but that's really a guaranteed spec under all rated conditions, so in reality, it lasts quite a bit longer. If you were to write the same page once a second, you'd use it up in a bit more than a day.
However, in real life, the "failure" criteria is when a page written with a test pattern doesn't read back as "erased" in a single readback. Simple enough, except that flash has transient read errors: that is, you can read a page, get an error, read the exact same page again and not get the error. Eventually, it does return the same thing every time, but that's longer than the "first error".
There's also a very strong non-linear temperature dependence on life. Both in terms of cycles and just in terms of remembering the contents. Get the package above 85C and it tends to lose its contents (I realize that the typical SSD won't be hot enough that the package gets to 85C, although, consider the SSD in a ToughBook in Iraq at 45C air temp..)
In actual life, with actual flash devices on a breadboard in the lab at "room temperature", I've cycled SLC NAND for well over a million cycles (hit it 10-20 times a second for days) without failure. This sort of behavior makes it difficult to design meaningful wear leveling (for all I know, different pages age differently) and life specs, without going to a conservative 100k/page uniform standard, which, in practice, grossly understates the actual life.
What you really need to do is buy a couple drives and beat the heck out of them with *realistic* usage patterns.
So then you only use magnetic tape for storage?
How long does it take to boot from that?
I have backups, so I can always restore.
SSD should work at maximum of 75% of their capacity... 50% or less is recommended
some chips try to move blocks to rotate the writes, have a lot of spare zones, so it can remap/use other sectors on write... but that is a problem, working in a full SSD will shorten its live
Higuita
No, magnetic tape is too vulnerable to EMP. He boots from punch card.
Fire susceptible.
I've implemented a filesystem on top of OpenCV that uses a laser to read bits carved into granite slabs.
If the laser fails, various sun alignments will allow the passive CdS sensor to take over, at a performance penalty of several years (about one IOP per year).