[BBLISA] Whatever happened to Seagate?

[Edward Ned Harvey (bblisa4)]

> From: bblisa [mailto:bblisa-bounces at bblisa.org] On Behalf Of Edward Ned
> Harvey (bblisa4)
> 
> For magnetic material, the degradation is "self-demagnetization" which
> occurs when adjacent bits oppose each other, and slowly cause one or both
> bits to neutralize each other.
> 
> For both magnetic material and flash material, the way to refresh the data is
> to read and re-write the data to the medium periodically.

Oh, um - 

Remember, the same is true for *all* bits. Not just the bits you stored offsite. This means, in your active hard drive or SSD that your OS boots from, any blocks that get written once early in the life cycle of the device, and then never overwritten again, suffer the same problem as archived storage media. This should give you some gut-feel estimates of how reliable the storage is.

So ... Your partition table, boot blocks, parts of the OS that don't get replaced by automatic updates over time, hardware drivers... Any of that stuff that remains static for the life of the device... All suffer from material deterioration, even though you have it powered on and constantly being used in your laptop or server.

In flash, there's something called "read disturb," which means, each time you read a cell, a few of the stored electrons are bled out, accelerating the normal leakage process. A good drive will keep track of this, and silently refresh blocks behind the scenes as necessary. So a good SSD can be maintained by periodically powering it on and then *reading* all the data; no need to rewrite.

I have no idea how you could lookup and verify which drives support that. It *may* be industry standard in all drives now. Or may not.