Why I'm usually unnerved when modern SSDs die on us

Post by dogecoinbase » Tue, Dec 11, 2018, 6:19 PM UTC

hwillis wrote: post #100

cyphar wrote: post #43

Earlier quoted context omitted.

> skates of magnetic readers flying on a cushion of air above a rapidly rotating disc, with the gap separating a few dozen nanometers, often smaller than the process size in the controller's silicon. Complete aside, the fly-height of a magnetic head is actually fractions of a nanometer (i.e. hundreds of picometers). EDIT: I got this from a talk by Bryan Cantrill[1]. The fly-height is allegedly 0.8 nanometers (800 pic…

I do not believe that. 1. I can't find a source that says less than a few nanometers. 2. 300 picometers is roughly the diameter of a helium diatom. The head cannot possibly float through hydrodynamic means if an air molecule can barely even fit under it.

Post by loeg » Tue, Dec 11, 2018, 6:20 PM UTC

godzillabrennus wrote: post #99

loeg wrote: post #93

Earlier quoted context omitted.

Users and administrators almost certainly prefer a 20 minute IO latency over data corruption. Host operating systems should probably flag an IO as failed long before 20 minutes and then you know 1) nothing made it to disk and 2) have some chance to avoid introducing additional corruption, if e.g., the OS is smart enough to kick out the drive when this happens. > Another problem is that the job while rewarding is not…

As someone that identified a bug in a Drobo firmware once and was offered a job on the spot I think the problem with attracting talent is two fold. The first problem is really two parts, not only is it rare to find people who have passion for storage related technologies but very few will gain exposure to these technologies to develop that passion. Kids don't routinely grow up with a SAN in the house. They do tend to…

Post by loeg » Tue, Dec 11, 2018, 6:21 PM UTC

xyzzy_plugh wrote: post #101

loeg wrote: post #93

Earlier quoted context omitted.

Users and administrators almost certainly prefer a 20 minute IO latency over data corruption. Host operating systems should probably flag an IO as failed long before 20 minutes and then you know 1) nothing made it to disk and 2) have some chance to avoid introducing additional corruption, if e.g., the OS is smart enough to kick out the drive when this happens. > Another problem is that the job while rewarding is not…

Both, and usually significantly. Last I checked it was nearly twice as lucrative to be a Ruby-on-rails developer than an embedded engineer. Embedded also attracts a certain type of engineer, usually very smart and able to manage extreme complexity with attention to detail but at the cost of anything resembling readable, let alone maintainable, software. The fact that anything at all works in the modern world is amazi…

Post by lisper » Tue, Dec 11, 2018, 6:25 PM UTC

notatoad wrote: post #97

lisper wrote: post #63

This is not a technological problem, it's a cultural one. These problems are easily fixed ("easily" by the standards of technical problems that regularly get fixed in other regimes). The reason they don't get fixed is that the customer reaction to failures like this is to rant at the mysterious storage gods that are making their lives miserable. Needless to say, there are no mysterious storage gods. These are artifac…

Physical devices don't have SLAs, because they aren't services. SSDs have the physical equivalent of an SLA, a warranty. I haven't seen stats, but in my experience the odds of an SSD dying within the warranty period is very very low. If you want your storage to have an SLA, storage service providers exist, and will be happy to give you an SLA if you're willing to pay. But it isn't cheap.

Post by blattimwind » Tue, Dec 11, 2018, 6:34 PM UTC

niftich wrote: post #21

Not that spinning HDDs are really any different, but SSDs are a perfect example of an entire computer that you attach to yours, and speak with through one of the (many) storage-oriented protocols. The device itself is a black box, and complex transformations take place between the physical persistence of the data and the logical structures that are exchanged on the wire. There are many layers of indirection, and many…