4 ms·

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

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

organicfigs 6y ago
Oh my god this book is amazing! Thank you
wtallis 6y ago
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 Their numbers for NAND page and especially erase block sizes are very outdated; more modern values are 4kB to 16kB for NAND pages and 16-24MB for erase blocks on TLC NAND.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.
ignoramous 6y ago
> 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.wisc.edu/~remzi/OSTEP/ https://web.archive.org/web/20200122013800/https://pages.cs....

organicfigs 6y ago

Oh my god this book is amazing! Thank you

wtallis 6y ago

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 Their numbers for NAND page and especially erase block sizes are very outdated; more modern values are 4kB to 16kB for NAND pages and 16-24MB for erase blocks on TLC NAND.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.

ignoramous 6y ago

> 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.wisc.edu/~remzi/OSTEP/ https://web.archive.org/web/20200122013800/https://pages.cs....