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Comment by sahil-kang | Hacker News Reader

I just finished reading the OSTEP book[1] and it has a nice chapter on SSDs[2]. The entire last portion of the book is about filesystems/disks so you might find it interesting.

[1] http://pages.cs.wisc.edu/~remzi/OSTEP/

[2] http://pages.cs.wisc.edu/~remzi/OSTEP/file-ssd.pdf

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That chapter on SSDs looks pretty good to me. Their numbers for NAND page and especially erase block sizes are very outdated; more modern values are 4kB to 16kB for NAND pages and 16-24MB for erase blocks on TLC NAND. Section 44.9 on mapping table sizes is a little bit odd, because most SSDs really do have 1GB of RAM per 1TB of flash, and that expense is widely seen as worthwhile even for multi-TB SSDs. The exceptions are low-end consumer SSDs that cache only part of the mapping table in a smaller amount of DRAM or SRAM, and a few enterprise/datacenter models that use 32kB block sizes for their FTL instead of the typical 4kB and thus reduce the DRAM requirement by a factor of 8 at the expense of greatly lowered performance and increased write amplification when writing in units smaller than 32kB.

Aside from the two above issues, everything looks correct and relevant, and I can't think of any missing details that deserve to be added to an introduction of that length.

> pages.cs.wisc.edu/~remzi/OSTEP

I see a maintenance page instead:

"Sorry! The URL you requested was not found on our server.

Is it Sunday between 4 and 8 PM (CST)? If so, the server may be undergoing regularly scheduled downtime. Otherwise, please contact the maintainer of the referring page and ask them to fix their link. Thanks!"

Here's a Jan, 2020 snapshot: https://web.archive.org/web/20200122013800/https://pages.cs....

Oh my god this book is amazing! Thank you

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