Pragmatic 7A: A Category Called General Follow-up 1

12 January, 2014


Follow up (Part A) to A Category Called General with some discussion about the expected lifespan of flash storage.
Transcript available
This is pragmatic follow-up part a episode seven a categorical general and that Alexandra Michael hosted John Geagea they spend are in this stuff follow-up for rather episode seven I asked or rather I lamented the fact that I couldn't find any detailed information about shelf life of flash drives and our Michael Wortley are once again are sort of to the rescue there and sent through a link to a house stuff works article link is in the show notes for this follow-up episode and this article suggested a 5 to 10 year shelf life so our thanks very much for Mike after sending that in in addition to that I did some more digging and found some more other interesting links I've also included and are in particular there is an Ars Technica our comments read and in particular the comment by Peter and the only information I got on him are suggested 10 years which sort of alliance with that the article that's our Mike sent me as well and the issue seems to be as I may have may not have alluded to is the difficulty in Excelerator life testing because normally if you're trying to do a LT on a product to determine its long-term lifespan normally focusing on temperature cycling and the problem is that not all whereat mechanisms affect our little whereat mechanisms driven by thermal cycling a lot of them are but but not all of them and sometimes it's difficult to know with a degree of certainty so there it is another method that sometimes referred to as her heat soak whereby you run the equipment at an elevated temperature for a significant period of time and what you do is you make an estimate of how many hours it would ordinarily experience a high temperature on a given day and statistically you can then projects if it fails after 100 hours that's the equivalent of 10,000 hours or something equivalent mass obviously depends on the technology but you that that might be might be a way of testing because the problem is that because the charge is stored the way the charge is stored in the flash disk eventually it's going to leak out eventually you're going to lose data and there is no question about that is just a matter of how long and there are a couple of ideas I thought were worth mentioning that either I was reading up about and one of the ideas is that if you are gonna use a flash disk every time you write to a flash disk in essence you are damaging are its ability to contain the charts every time you reflash it every time you update the data in an that the one I get around that as they build in additional capacity into the flash disk so they say okay well I'm an account for our another 5% loss and therefore I'll write my drive at the oversized my drive by 5% I'm not sure the exact figure is but I'm sure it varies from manufacturer to manufacturer the idea is that they shift the data around to ensure that everything gets an equal amount of wear and they flagged bag bad pastor don't go back and so, inflating bad sectors are kind of idea and eventually you'll get to a point where everything is had so much aware that it can't reliably hold data and that's that's the problem with flash so and it's different depending upon its MLC or SLC and Donna gone too much depth and that but just just take my word for it is a different technology used for different kinds of flash sulphite is created equal again might do a show about that later but anyway the point is that if you are trying to store data on a flash disk for long-term shelf storage your best bet is to go for a new and either a new or near new flash drive that has had minimal rewrites done to it was a rewrite I should say just flash rights to it some other words I would be buying a flash drive writing the data I tend to store long-term on take the drive output on the shelf and not touch again there is also a suggestion that because the charge will leak out over time it may be advantageous to do a data refresh our every 2 to 3 years to ensure the data integrity so in such a case you might get our storage and when I say do a complete refresh I mean literally completely read it and then completely rewrite it so is not enough to read the data needs to be flashed and then flash back if you honour me so and that should then reinforce those are reinforce those are bits such that they would then maintain integrity for theoretically for longer but again it very conflicting reports on how often you should do that and the truth is that the technology is just is very new we've got a lot of history on hard drives we got even more with floppy disks in an Magna end and flexible magnetic media we got plenty with optical discs although Blu-ray is still relatively young in in the other sort of terms but similar enough technology to CERN DVD-R that we can make intelligent assumptions based on our knowledge of their lifespans so I'm sure as the case will come out in the next three or four years as flash drive capacities increased we reach a point where we can say well data is still present after 789 years therefore using this technology we expect to maximise better say 15 years the number should increase how much they increase to I don't know but I would not expect flash to outlast AER a Blu-ray disc for example I wouldn't expect flash to outlast even some hard drives maybe and certainly not I don't expect flash would would would last as long as AM 35 year lifespan tape as we discussed on the show so in any case it's in it's interesting and is it personally I would be using them for long-term data storage until we have more information about how their what their longevity is a shelflife is one of the expanse story at this point while absolutely you can't store large amounts of data and an EOU glass question why would you in the first place but I just wanted to make sure that we covered off as an option because there are still cases what for example we had a project that I did when I was working for arm a large consultancy and when we went into the project at the end of it the client specifically asked for a flash drive with all the project data right and fair enough it was you know about for 5 GB but then the over 16 gig flash drivers but five bucks is not a lot of money if that apparently I doubt I'll the reference to what the app yes you're right they are there everywhere there there everywhere now so we did that for them and resource that I'll DO here go in that was to be for their long-term storage now gonna keep on file keep a copy on their own servers alive copy essentially they can access when they had to and this is only their backup and assess what they want to do so I don't suggest that individuals must backup their entire collection of arm photos of gigabytes of photos these things because it's too expensive but someone may have a library that is a reasonable size have a flash this lying around I think they're covered my guess Mac OS and I just advise caution muscle make monitoring in Frankfurt primarily tax documents you could panic multiple could get everything they reasonably need into a single one of those owners and there is AER a reassuring our aspect of their little keychain like size that's true so are in any case thank you Mike for that feedback much appreciated where around and are yet I don't I don't do much more else to say about that´┐Ż
Duration 8 minutes and 15 seconds Direct Download

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Ben Alexander

Ben Alexander

Ben created and runs and Fiat Lux

John Chidgey

John Chidgey

John is an Electrical, Instrumentation and Control Systems Engineer, programmer, podcaster and runs TechDistortion and the Engineered Network. John has produced and appeared on many podcasts as well as Pragmatic.

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