https://www.vidarholen.net/contents/blog/?p=479 tl;dr: dd works for reading and writing disks, but it has no "low level I/O" capabilities that make it more suited for this than any other shell utility. Like cat you should use it where it makes sense, e.g. to take advantage of its wide array of options, rather than try to ensure that all disk related commands begin and end with dd out of fear and superstition.

1.25K views09:00

fc fs筆記

https://lore.kernel.org/linux-btrfs/20231217165359.604246-1-hch@lst.de/ host-aware SMR hdd 從 SCSI / ATA 標準中刪掉了(NVMe 標準中沒有加過)，今後就只會有 host-managed 和 device-managed SMR 了。 Linux 內核會把現存少量的 host-aware SMR 設備當作 device-managed SMR （OS 看來是普通的 HDD ）用

1.31K viewsfarseerfc 😂, edited 03:16

fc fs筆記

https://www.evanjones.ca/durability-nvme.html
關於 NVMe 設備上寫入的語義的一些解讀，引用到了 NVMe 標準，對不想細讀標準是一個不錯的總結

🥰4

647 viewsfarseerfc 😂, 08:31

fc fs筆記

rst-linux-paper.pdf
https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/rst-linux-paper.pdf

👍4

435 viewsfarseerfc 😂, 05:21

fc fs筆記

rst-linux-paper.pdf https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/rst-linux-paper.pdf

Intel RST 在 linux 上用 mdadm 的文檔

457 viewsfarseerfc 😂, 05:21

fc fs筆記

Forwarded from Linux - Reddit

Understanding Unix filesystem timestamps
https://unixdigest.com/articles/understanding-unix-filesystem-timestamps.html

https://redd.it/1j8jhvt
@r_linux

👍4

351 viewsfarseerfc 😂, 05:45

fc fs筆記

https://despairlabs.com/blog/posts/2025-03-13-fsync-after-open-is-an-elaborate-no-op/ fsync 具體行為有多模糊

despair labs

fsync() after open() is an elaborate no-op

I have spent the last couple of years of my life trying to make sense of fsync() and bringing OpenZFS up to code. I’ve read a lot of horror stories about this apparently-simple syscall in that time, usually written by people who tried very hard to get it…

🤔3

515 viewsfarseerfc 😂, 02:16

fc fs筆記

https://despairlabs.com/blog/posts/2025-03-13-fsync-after-open-is-an-elaborate-no-op/ fsync 具體行為有多模糊

Linux and ext4 however does not (or at least, didn’t used to). It used to both clear the error state and mark the page clean, but valid. In all respects it looked like a page freshly read from disk. But, that data was not on disk (the write failed!), any attempt to flush it would do nothing (it’s not dirty). But, because it’s a clean page, it’s eligible for eviction, resulting in the weird situation that you could read data from it and it “worked”, and read it again later and it faults. This is all perfectly legal, and I imagine more efficient in some situations – if it’s clean then there’s no I/O to do, but if it’s valid there’s no fault to process.
And our program would never know, because it misunderstood what a successful fsync() meant.

原來 ext4 上 fsync 還有這種行為…

😱2

399 viewsfarseerfc 😂, edited 02:17