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SSD Write Endurance Considered Sufficient

ef.gy

1–10 of 34 posts

Re: SSD Write Endurance Considered Sufficient

#3
post #2

It looks like he's only considering ideal writes with no amplification. This can make a big difference: http://lwn.net/Articles/428584/

Considering he's modeling the drive writing at the full SATA 3.0 interface speed for the entire lifespan of the drive, continuously, amplification shouldn't affect his numbers, only the perceived throughput the user receives under this workload. He mentions this is already faster than the drive can actually write: "the maximum link speed for SATA 3.0, which happens to be larger than any other relevant interface or drive speed so it's a solid upper bound."

Re: SSD Write Endurance Considered Sufficient

#4
This is a pretty poor article. Consumers haven't bought SLC in years and MLC is much less reliable (although the actual reliability of flash is still higher than the rating). It doesn't take write amplification or any kind of real workload into account. And it may contribute to the alarmism that it claims to dispel; at worst your SSD will last 172 days? Yikes!

Re: SSD Write Endurance Considered Sufficient

#5
People go completely irrational about avoiding writes to SSD's, I've seen researchers at an EE dept spending evenings tuning their Windows installations and going as far as stuffing frequently used stuff onto a RAM disk.

I guess the early off brand SSD's randomly eating your data didn't help the popular perception (even though that wasn't because of flash wear). But still...

Re: SSD Write Endurance Considered Sufficient

#6
tl;dr

I'm guilty of the SSD fear. My first Intel (320) drive was meticulously maintained in fear of shortened life span and performance losses. I went so far as to question every file copied to the drive vs. mounting an external HDD. The thing bricked itself due to a firmware bug in less than 12 months.

Using a Samsung drive now. I don't think about read/writes anymore. I just use the darn thing.

Re: SSD Write Endurance Considered Sufficient

#7
post #3
post #2

It looks like he's only considering ideal writes with no amplification. This can make a big difference: http://lwn.net/Articles/428584/

Considering he's modeling the drive writing at the full SATA 3.0 interface speed for the entire lifespan of the drive, continuously, amplification shouldn't affect his numbers, only the perceived throughput the user receives under this workload. He mentions this is already faster than the drive can actually write: "the maximum link speed for SATA 3.0, which happens to be larger than any other relevant interface or dr…

I thought write amplification happened inside the drive (due to the drive internally working in bigger blocks than the 512-byte sectors it presents to the outside world), so the amount of data written to flash would be greater than the amount sent over the SATA link?

Re: SSD Write Endurance Considered Sufficient

#8
post #4

This is a pretty poor article. Consumers haven't bought SLC in years and MLC is much less reliable (although the actual reliability of flash is still higher than the rating). It doesn't take write amplification or any kind of real workload into account. And it may contribute to the alarmism that it claims to dispel; at worst your SSD will last 172 days? Yikes!

Not like magnetic is necessarily immune. WD greens used to have astoundingly bad spin down logic. I killed a bunch of them with default Linux settings and near idle servers in about that time frame.

Re: SSD Write Endurance Considered Sufficient

#9
post #4

This is a pretty poor article. Consumers haven't bought SLC in years and MLC is much less reliable (although the actual reliability of flash is still higher than the rating). It doesn't take write amplification or any kind of real workload into account. And it may contribute to the alarmism that it claims to dispel; at worst your SSD will last 172 days? Yikes!

While I completely agree, I think it is important to point out that SLC is still used pretty widely in Enterprise-grade SSDs. Standard configuration on these drives is 100% over-provisioning, so lifespan is likely 20+ years.

Re: SSD Write Endurance Considered Sufficient

#10
I've always wondered what these theoretical numbers, which has been quoted since long before consumers could ever afford an SSD, should tell you... They should not, in any way, make you trust your SSD. They are beyond useless. Also, this article assumes no write amplification and assumes perfect wear level algorithms. He/She even throws in usb-thumb drives in the mix, so, how do you know if your thumb drive has a perfect (TM) wear level algorithm? What about that flash card? Would you recommend storing swap and log files on that too? Sigh.

Compared to this article the advice of not ever storing swap/log files on a flash drive would be sound advice.

But yes, you are probably not going to hit the limits of your consumer drive SSD. But whether you are going to or not you will not, under any circumstances, be able to find out by making some numbers up. If anyone knows it is the manufacturer, and you can bet you won't get access to that data.

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