4 ms·

SSD Write Endurance Considered Sufficient

41 points by forbes 14y ago

jbellis 14y ago
It looks like he's only considering ideal writes with no amplification. This can make a big difference: http://lwn.net/Articles/428584/ http://lwn.net/Articles/428584/
- jerf 14y ago
  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."
  - tbrownaw 14y ago
    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?
wmf 14y ago
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!
- danielvinson 14y ago
  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.
- jws 14y ago
  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.
  - pasbesoin 14y ago
    I have a Scorpio Blue that parked its heads incessantly until I deployed a utility to force better ACPI settings. Not write endurance, per se. But you only get to park the heads so many times, on average...
    - jws 14y ago
      Yeah, statistics work. I had greens fail at 30k parks and survive over 1M parks. 300k was the published number for parks. I think they screwed up by allowing the firmware to thrash them to death, but I think they got the 300k number right.
      - pasbesoin 14y ago
        Do you have any concrete/verified descriptions of the firmware problems? I ran across plenty of people commenting on the problem, and my own intuition (or deduction, based on listening to the "click... click... click..." and eventually noting the escalating number of parks reported) plus the fix that worked for me strengthened this intuition. But I never saw a documented analysis let alone an admission on WD's part. (Admittedly, I may have missed one or both.)
  - drzaiusapelord 14y ago
    Greens are not enterprise drives and shouldn't be used in RAID arrays. Their logic makes perfect sense for single disk and "green" (power saving.) Its just incredible what people will do to save a little cash on servers. Your company's data depends on them and you put in the cheapest Best Buy inventory you can find?
    - wmf 14y ago
potkor 14y ago
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...
- marshray 14y ago
  What's wrong with locating frequently used stuff on a RAM disk?
  - wmf 14y ago
    It's work, but it's unlikely to have any benefit.
lbraasch 14y ago
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.
- threedaymonk 14y ago
  > The thing bricked itself due to a firmware bug in less than 12 months. Was it an OCZ, by any chance? The exact same thing happened to me. I scrupulously avoided unnecessary wear, disabled swap (though I've been disabling swap for years), mounted /tmp on a RAM disk, and the accurs't thing killed itself stone dead waking from sleep due to a firmware bug. I also replaced it with a Samsung, as it happens.
  - ryanklee 14y ago
    > My first Intel (320) drive
    - threedaymonk 14y ago
      Oh, that's embarrassing! I read that, but somehow convinced myself that it was part of another comment.
- specto 14y ago
  I don't worry much about my ssd, however I do occasionally look at the wear with smartools.
- drzaiusapelord 14y ago
  The 320 had a brickable fw bug? I have 5-10 or so in production and have no issues. Maybe mine have a newer FW. I always update them when I give them out.
  - 14y ago
tjoff 14y ago
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.
- twotwotwo 14y ago
  You can use smartctl or equivalent to see the media wear indicator. But SSD firmware bugs have been a larger problem in practice than wearout, and MWI won't help you with them; keep backups.
gcp 14y ago
c't has a lang duration test where it became obvious many SSD's were dying long before they should according to the theoretical numbers. Unfortunately it doesn't seem to be available for free: https://www.heise.de/artikel-archiv/ct/2012/03/066_SSD-Zerstoerung https://www.heise.de/artikel-archiv/ct/2012/03/066_SSD-Zerst... This technology is too dependent on software to make these kind of models even remotely approximate reality.
- 65a 14y ago
  Here's a forum doing write tests on a variety of mlc and slc drives...ongoing: http://www.xtremesystems.org/forums/showthread.php?271063-SSD-Write-Endurance-25nm-Vs-34nm http://www.xtremesystems.org/forums/showthread.php?271063-SS... Also, most MLC has between 10k and 1k writes, not 100k. TLC is even worse!
saidajigumi 14y ago
SSD write fear is kinda nuts, IMO. It's a device subject to wear, tear, and catastrophic failure -- just like HDDs. Keep backups (three for important data; a cloud copy is only one copy), enjoy the performance, and don't sweat it. If you aren't keeping backups, then go ahead and cower under the sheets at night.
- twotwotwo 14y ago
  - Smartctl has a media wearout indicator if you want to check. Most likely, you'll check it after months of use, see that you've used like 3% of the write capacity, and then not sweat it. - Firmware reliability sadly has been an issue. So, yes, keep backups. - It's fun to check out the ongoing SSD write exhaustion derby here: http://www.xtremesystems.org/forums/showthread.php?271063-SSD-Write-Endurance-25nm-Vs-34nm http://www.xtremesystems.org/forums/showthread.php?271063-SS...
deleted 14y ago
[deleted]
bconway 14y ago
I remember when SSD's first started hitting the market years ago, everyone's utmost concern was about wear leveling. As it turns out, if you ship a drive with buggy firmware and it refuses to be recognized after the 50th cold boot, write leveling ends up not being so important.
twotwotwo 14y ago
SMART says the years-old, low-capacity MLC SSD in this computer is 5% worn out. SSDs in RAID arrays at work are getting a much heavier workout and handling it fine. You can use smartctl or the equivalent to check the media wearout indicator to see how much the actual workload has worn out a drive. If your computer isn't constantly writing, you're probably fine--that is, your writes will last until you'd be upgrading anyway. But, keep backups. Besides the many practical problems you can have (laptop lost! fire!), SSDs have firmware bugs every so often.
rnovak 14y ago
Since when do SSD's have a 100,000 write limit? My 256gb Samsung 840 has something like 2-3k, not 100k.
- wmf 14y ago
  SLC. This article is a blast from the past.

41 points by forbes 14y ago

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

jerf 14y ago
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."
- tbrownaw 14y ago
  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?

wmf 14y ago

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!

danielvinson 14y ago
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.
jws 14y ago
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.
- pasbesoin 14y ago
  I have a Scorpio Blue that parked its heads incessantly until I deployed a utility to force better ACPI settings. Not write endurance, per se. But you only get to park the heads so many times, on average...
  - jws 14y ago
    Yeah, statistics work. I had greens fail at 30k parks and survive over 1M parks. 300k was the published number for parks. I think they screwed up by allowing the firmware to thrash them to death, but I think they got the 300k number right.
    - pasbesoin 14y ago
      Do you have any concrete/verified descriptions of the firmware problems? I ran across plenty of people commenting on the problem, and my own intuition (or deduction, based on listening to the "click... click... click..." and eventually noting the escalating number of parks reported) plus the fix that worked for me strengthened this intuition. But I never saw a documented analysis let alone an admission on WD's part. (Admittedly, I may have missed one or both.)
- drzaiusapelord 14y ago
  Greens are not enterprise drives and shouldn't be used in RAID arrays. Their logic makes perfect sense for single disk and "green" (power saving.) Its just incredible what people will do to save a little cash on servers. Your company's data depends on them and you put in the cheapest Best Buy inventory you can find?
  - wmf 14y ago

potkor 14y ago

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...

marshray 14y ago
What's wrong with locating frequently used stuff on a RAM disk?
- wmf 14y ago
  It's work, but it's unlikely to have any benefit.

lbraasch 14y ago

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.

threedaymonk 14y ago
> The thing bricked itself due to a firmware bug in less than 12 months. Was it an OCZ, by any chance? The exact same thing happened to me. I scrupulously avoided unnecessary wear, disabled swap (though I've been disabling swap for years), mounted /tmp on a RAM disk, and the accurs't thing killed itself stone dead waking from sleep due to a firmware bug. I also replaced it with a Samsung, as it happens.
- ryanklee 14y ago
  > My first Intel (320) drive
  - threedaymonk 14y ago
    Oh, that's embarrassing! I read that, but somehow convinced myself that it was part of another comment.
specto 14y ago
I don't worry much about my ssd, however I do occasionally look at the wear with smartools.
drzaiusapelord 14y ago
The 320 had a brickable fw bug? I have 5-10 or so in production and have no issues. Maybe mine have a newer FW. I always update them when I give them out.
- 14y ago

tjoff 14y ago

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.

twotwotwo 14y ago
You can use smartctl or equivalent to see the media wear indicator. But SSD firmware bugs have been a larger problem in practice than wearout, and MWI won't help you with them; keep backups.

gcp 14y ago

c't has a lang duration test where it became obvious many SSD's were dying long before they should according to the theoretical numbers. Unfortunately it doesn't seem to be available for free: https://www.heise.de/artikel-archiv/ct/2012/03/066_SSD-Zerstoerung https://www.heise.de/artikel-archiv/ct/2012/03/066_SSD-Zerst... This technology is too dependent on software to make these kind of models even remotely approximate reality.

65a 14y ago
Here's a forum doing write tests on a variety of mlc and slc drives...ongoing: http://www.xtremesystems.org/forums/showthread.php?271063-SSD-Write-Endurance-25nm-Vs-34nm http://www.xtremesystems.org/forums/showthread.php?271063-SS... Also, most MLC has between 10k and 1k writes, not 100k. TLC is even worse!

saidajigumi 14y ago

SSD write fear is kinda nuts, IMO. It's a device subject to wear, tear, and catastrophic failure -- just like HDDs. Keep backups (three for important data; a cloud copy is only one copy), enjoy the performance, and don't sweat it. If you aren't keeping backups, then go ahead and cower under the sheets at night.

twotwotwo 14y ago
- Smartctl has a media wearout indicator if you want to check. Most likely, you'll check it after months of use, see that you've used like 3% of the write capacity, and then not sweat it. - Firmware reliability sadly has been an issue. So, yes, keep backups. - It's fun to check out the ongoing SSD write exhaustion derby here: http://www.xtremesystems.org/forums/showthread.php?271063-SSD-Write-Endurance-25nm-Vs-34nm http://www.xtremesystems.org/forums/showthread.php?271063-SS...

deleted 14y ago

[deleted]

bconway 14y ago

I remember when SSD's first started hitting the market years ago, everyone's utmost concern was about wear leveling. As it turns out, if you ship a drive with buggy firmware and it refuses to be recognized after the 50th cold boot, write leveling ends up not being so important.

twotwotwo 14y ago

SMART says the years-old, low-capacity MLC SSD in this computer is 5% worn out. SSDs in RAID arrays at work are getting a much heavier workout and handling it fine. You can use smartctl or the equivalent to check the media wearout indicator to see how much the actual workload has worn out a drive. If your computer isn't constantly writing, you're probably fine--that is, your writes will last until you'd be upgrading anyway. But, keep backups. Besides the many practical problems you can have (laptop lost! fire!), SSDs have firmware bugs every so often.

rnovak 14y ago

Since when do SSD's have a 100,000 write limit? My 256gb Samsung 840 has something like 2-3k, not 100k.

wmf 14y ago
SLC. This article is a blast from the past.