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Comment by joshvm | Hacker News Reader

This is encouraging although even tests on early drives showed that an 'average' drive should last far longer than people need them for - purely based on the number of allowed writes. 750TB? That's more data than my department, an imaging research group, have on our cluster...

There are some more tests which are very hard to do because you need time and a large sample size, for instance what's the data retention time for a typical SSD?

As far as I can tell, nobody really knows because you'd need to leave the drive off for probably more than a year - and as soon as you turn the drive on, presumably you refresh the charge that's leaked out? Most of the time this isn't a problem because almost everyone turns on their PC or laptop weekly/monthly if not daily.

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> as soon as you turn the drive on, presumably you refresh the charge

No, bits lose their charge slowly but it doesn't matter whether the SSD is powered on or off. http://www.tomshardware.com/forum/256180-32-read-longevity

As a side note, the really interesting thing about this endurance test is that almost all the drives fail badly at the end of their life. Even though almost all the manufacturers specifically claim they "fail safe" into a read-only mode.

It's frequently assumed that breakdowns are geometric random variables and we can extrapolate the rate by testing many drives. For example, test 100 drives.and find when the first one breaks.

The numbers in this test should be interpreted as an average with some drives breaking earlier. Now consider the failure rates for drives where the file is spread across multiple disks.

If you don't have much RAM I suppose you'd hit these limits much faster as OS would swap a lot of data onto drive.

Two of the drives survived a year of continuous use, so even regular swapping is trivial.

Say you're using your computer 12 hours a day, half of that doing tasks where memory usage greatly exceeds your physical memory, and you're using 1/4 of the bandwidth of the drive to swap in/out (of which 1/2 are writes).

Under this quite heavy scenario, the writes will catch up to this endurance test after 32 years.

The speed, price & capacity of these drives are (at least for now) improving so quickly that by the time you wear one out, even with torturous use, replacing it will be trivial.

Cost per gigabyte has halved over the period of this test. So even when taking the drive that just died and using it for the most pathological use case imaginable, you'd be buying a $200 drive today, replacing it with a $100 drive in one year, $50 in two years, etc. Not a big deal.

I just wish someone could tell me one I could buy that would last longer than 1.5 years in my laptop. I'm on #3 now :(

The 100 "GB" OCZ Vertex LE in my laptop has 27,834 hours of power-on time. This is the only drive in the system, and it houses several always-on encrypted swap partitions. I'd be surprised if you could purchase a new one at this time, though. :P

I can get back to you in a little more than a year about the 750 "GB" Samsung 840 EVO in the lady's laptop, and 6->8 months on the Crucial M4 SSD in my gaming PC. :)

My last to fail was an OCZ Vector :(

Any of the Intel SSDs should last you the life of the laptop.

I prefer $brand, they hold up better under extensive use.

If you're swapping regularly then you have more immediate computer needs than a fast hard drive.

I actually wish I could turn swap off safely on my work computer, because I actually have enough RAM for normal situations. Swap may eventually be an old curiosity for most people, and a "niche thing" for others... When I start swapping, it's a sign some application is leaking memory and I'd rather it didn't get any and crashed instead of freezing the machine up for ages while trashing the drive.

But as it turns out OS X behaves really badly if you try to take away its swap (last time I tried, the kernel memory usage slowly increased until it consumed almost all memory; I re-enabled flash and rebooted and it got back to normal. It's a bit annoying that we've become so dependent on a kludge to work around too little memory. (Brings me back to my Amiga days and the long, heated discussions about whether or not swap was a good idea in the first place)

One trick people in a similar situation on linux use is to make a small ram disk and then assign that as the swap. A little absurd but prevents the bad behavior.

It is indeed absurd, when swapping can be avoided entirely by setting kernel swappiness to 0:

sysctl -w vm.swappiness=0

to make permanent, set vm.swappiness=0 in /etc/sysctl.conf

Though for a desktop machine, disabling swap probably won't help improve performance

That's true, but this was a special circumstance where disabling swap was creating very bad system behavior.

pre 3.5 it doesn't actually disable swap, it will only use it when it's about to OOM.

post 3.5 it does actually hard-disable, but setting swappiness to 1 gives the same behaviour as swappiness=0 in < 3.5

That's good to know, thanks.

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