Hybrid HDDs endurance: 1 year

[eMaCon]

Using a NAND flash as cache unit in a HDD? In my opinion, the problem is the max number of Program/Erase Cycles of a NAND flash memory (according to Samsung, Toshiba, ST Microelectronics, 100K Program/Erase Cycles). According to these numbers, a hybrid hard disk can last... let me chew some numbers... 1 year! Am I right?

 

[OCedHrt]

100K write/erase cycles? I'd be lucky if I get 1 day.

 

[TuxDave]

I wonder why it's so low.

 

[patentman]

The NAND flash memory is currently being developed to cache what is existing on your desktop, in your RAM, and your system settings when you shut your system off. The idea is that you can reboot your system to the state it was in much more quickly then having to load everything from the hard disk upon powering on your pc. Unless you are turning your computer on and off every 2-3 minutes I don;t really see how lifetime is going to be an issue.

 

[pm]

Good post, patentman. Thanks

 

[lexxmac]

Flash is being developed and shoved into all kinds of situations, and I can see where the failure rate on flash memory might be a problem. Flash does fail eventually...

 

[MrDudeMan]

Originally posted by: lexxmac
Flash is being developed and shoved into all kinds of situations, and I can see where the failure rate on flash memory might be a problem. Flash does fail eventually...

but it wont be an issue for the intended use of it in this application

 

[nismotigerwvu]

OK, lets see how my logic is on this......Hybrid drives use some flash memory (NAND in this case) and a traditional HDD. Is there any reason that the HDD couldn't function on its own when the flash memory dies out? Why not make the flash work on a socket and have remoavble/upgradable. That or why not use ddr1/2 instead, RAM, to me, seems better suited for this anyways

 

[byosys]

That or why not use ddr1/2 instead, RAM, to me, seems better suited for this anyways

I think part of the reasoning behind the use of flash storage is to keep (some of) the boot files in the cache so when you boot, you are loading the first few files (or all of them - depends on the size of the flash part) from flash memory instead of the hard drive (or you get to process the first few files while the hard drive spins up for the rest of them). This would not be possible using DDR 1/2 as you need to power the DDR for it to retain its contents. Thinking about using DDR, I can see it only being useful for a large prefetch buffer (similar to how a CPU makes an "educated" guess at the next command to be issued before said command arrives at the CPU). I have doubts as to how effective this would be in terms of performance in most desktop environments as hard drive usage tends to vary widely. Another problem with DDR is that if you have a file saved to the "hard drive", but it's really only in DDR, and you lose power, that file is now gone forever with no way to get it back. This is especially noteworthy if the DDR part of a harddrive is simply part of the overall hard drive to the OS.

 

[nismotigerwvu]

But the power issues could resolved using battery backup ala those "ram drives" (the comnpany/product name slips me now) and have a "oh crap" mechanism built in that once system power cuts out the ddr buffer is dumped asap to the hdd. Then you could use a driver of some sorts to moninter which files are most used most and create a priority system balancing out use and size ect ect. Worst case at this point would be needing to refill the ddr buffer should the power be cut long enough to kill the battery (and hopefully the "most used data tracker file thingy" would have been dumped to the hdd anyways) so you might have a slow boot the first time on or may just have a puase after posting while the biffer gets refilled...the downside to using ddr could be heat, as hdd's make enough already and flash does run a ton cooler....I'm just throwing this out for conversation, not trying to put anything down. Beisdes, if ddr was the way to go I'm pretty sure companies would have already taken that route

 

[lexxmac]

According to wikipedia, commercially available flash is good for one million write cycles, and considering that you must erase and rewrite an entire block just to change one bit inside of it, flash will eventually fail. After several years in a heavy use environment, is it not a possibility that you are going to end up with blocks failing?