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possibilities with raw flash access

possibilities with raw flash access

Posted Aug 25, 2009 6:33 UTC (Tue) by markusw (guest, #53024)
In reply to: possibilities with raw flash access by dlang
Parent article: The trouble with discard

If you have access to the raw NAND device (i.e. an MTD device, not a block device as seen from the Linux kernel) the very first thing to use properly is block discard. The 'partial block reuse' technique described might improve things as well, but compared to block discard it can only be a minor optimization. Also keep in mind that block erasure is a specified operation which just needs to be used by the above layers. On contrary, I'm not quite convinced that 'overriding' of blocks is properly supported on all devices.

However, despite the mentioned Fusion-IO devices (and I'm not even sure about those, as they have proprietary drivers) I don't know any device for commodity computers which allows raw NAND access. I've only seen that in the embedded world - and there we normally speak of just one single chip with some MiBs of storage capacity. So this discussion is theoretical anyway.

Despite wanting to have raw access to NAND devices, I'm also wondering about the latency implications of the involved SATA protocol. Cutting that and attaching the NAND more directly to PCI Express certainly can't hurt.


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possibilities with raw flash access

Posted Aug 27, 2009 18:07 UTC (Thu) by robert_s (subscriber, #42402) [Link]

"I don't know any device for commodity computers which allows raw NAND access."

It's not pretty, but there used to be a USB XD card reader chip called alauda which would expose the XD/SM card ( they are both basically repackaged NAND chips ) as an MTD. Linux drivers are in the tree I think.

Useful for little more than experimentation. And only then if you're good at hunting for one on ebay.


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