121–130 of 258 posts
As densities of data get higher and higher, it doesn't take much to have a catastrophic data failure. The only way to protect against this is having multiple replicas of your data.
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…
> 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. These days most of what we call a computer could be described this way. Even your compiled machine language is ultimately far more abstracted from what the processor actually does than it was on, say, a 6502.
Funny that you bring up 6502; that reminds me of 1541 disk drive for C64, which had mostly same 6502 as the host computer (albeit running at slower speed).
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I have seen some weird issues with SSDs. I had an OCZ Vertex 2 die on me multiple times, but one thing that stood out most is that after a power cycle or complete system shutdown (note: reboots were just fine) everything I had done last time - install software, update Windows, create files - was gone. The state was reverted to before the time it booted. It was like my computer contained some kind of Reborn chip, exce…
Modern SSDs have incredibly large caches. For example, HP EX920, which is a TLC (triple layer cell) SSD, in its 1TB model contains a whooping 200GB of SLC (single layer cell) cache. It's entirely possible that your changes are simply in cache only, and hasn't been committed to the actual storage.
I worked on SSD firmware for quite a long time and here is my perspective. Early flash used to fairly reliable with almost minimal error correction. However with increasing density, smaller processes and multi level cells, it has gone progressively less reliable and slower. Here are some of the things that we need to worry about: https://www.flashmemorysummit.com/English/Collaterals/Procee... To compensate for all th…
> Another problem is that the job while rewarding is not very lucrative. The chance of a multi million dollar payoff for an employee is low. I have a higher chance working on a web connected gadget to become a millionaire. So that means it is really hard to recruit those who are top notch programmers who known how to figure out the algorithms, write the code, debug the hardware. Most new grads these days are interest…
I worked on SSD firmware for quite a long time and here is my perspective. Early flash used to fairly reliable with almost minimal error correction. However with increasing density, smaller processes and multi level cells, it has gone progressively less reliable and slower. Here are some of the things that we need to worry about: https://www.flashmemorysummit.com/English/Collaterals/Procee... To compensate for all th…
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What's involved in recovering the data if the controller fails?
just based on having seen data recovered from other flash devices, and the advertising copy of these devices: hot-air rework to lift all the flash chips off and get them hooked up to something (probably custom) that can read them. if the controller was encrypting everything that went to flash, you also get to try and find the key in the controller's memory.
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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…
I predict we will lose all of our engineers - embedded dudes included.
I worked at a storage company, and they reinforced to us how not only does the OS lie to us, but the hard drives also lie to the OS. So you can't take anything you get from a hard drive as reliable, you have to test the data once you get it, ex through CRC, etc. Data can get corrupt at any time. As densities of data get higher and higher, it doesn't take much to have a catastrophic data failure. The only way to prote…
OS: Yes, I did.
OS' inner voice: Nah, I didn't, but I'll do it soon, I think.
OS to drive: Those write commands, they're durable yet?
Drive: Sure!
Drive's inner voice: Nah, they're still in my RAM, but I'll probably write them out any time now.
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> 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. These days most of what we call a computer could be described this way. Even your compiled machine language is ultimately far more abstracted from what the processor actually does than it was on, say, a 6502.
> Even your compiled machine language is ultimately far more abstracted from what the processor actually does than it was on, say, a 6502 Funny that you bring up 6502; that reminds me of 1541 disk drive for C64, which had mostly same 6502 as the host computer (albeit running at slower speed).
A major problem with SSDs seems to be “firmware death” - where the flash chips are physically fine (or mostly fine), but the firmware (or firmware memory) has gotten corrupted due to some programming error, electrical glitch, or cosmic ray. I’ve had scores of older SSDs die after things like power outages and sudden shutdown events. This is super frustrating because the data is physically OK but the controller just i…
I have seen some weird issues with SSDs. I had an OCZ Vertex 2 die on me multiple times, but one thing that stood out most is that after a power cycle or complete system shutdown (note: reboots were just fine) everything I had done last time - install software, update Windows, create files - was gone. The state was reverted to before the time it booted. It was like my computer contained some kind of Reborn chip, exce…