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0 pointsrasz7mo ago0 comments

I dont buy this. There are plenty of dramless SATA SSDs which should be impossible if your description was correct, not to mention DRAMless drives working just fine inside USB-NVME enclosures.

>but gets huge for a modern SSD (1+GB per TB of SSD)

except most drives allocate 64MB thru HMB. Do you know of any NVME drives that steal Gigabytes of ram? Afaik Windows limits HMB to ~200MB?

>Finally, I'll point out that there's a lot of nonsense about DRAMless SSDs on the internet

FTL doesnt need all that ram. Ram on drives _is_ used for caching writes, or more specifically reordering and grouping small writes to efficiently fill whole NAND pages preventing fragmentation that destroys endurance and write speed.

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dijit7mo ago

but isn’t it the case that SATA devices must receive AT commands to the disk controller while NVMe is mapped directly to the CPU?

Surely that distinction would make one more vulnerable to corruption than the other?

Sesse__6mo ago

Are you talking about the fact that NVMe works by MMIO and DMA? So is pretty much any SATA controller, so there's no inherent difference there (there are _many_ years since the dominant way of talking to devices was through programmed I/O ports). Unless you have a NVM device with host-backed memory (as discussed elsewhere in the thread), it's not like the CPU can just go and poke freely at the flash, just as it cannot overwrite a SATA disk's internal RAM or forcefully rotate its platters. It can talk to the controller by placing commands and data in a special shared memory area, but the controller is fundamentally its own device with separate resources.

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