3 ms·
100s of milliseconds is the right order of magnitude.
by monocasa 5y ago
100s of milliseconds is the right order of magnitude.
- jlokier 5y agoI think at least 1-2 seconds. I measured the performance of different size direct I/Os on some Samsung SSDs, and the write performance when switching from one test to another was significantly affected by the previous test parameters, or not, depending on whether a "sleep 2" was inserted between each test. The only explanation I can think of is that the flash reorganises or commits cached data during that 2 seconds.
- wtallis 5y agoIf you were using consumer SSDs, you have multiple layers of caching to worry about: in the controller's SRAM, and in a portion of the flash that's operating as SLC. There are also power saving modes to consider; waiting long enough for the drive to drop to a sleep state means you'll incur a wakeup penalty on the next IO.
- marcan_42 5y agoIt's at least 5 seconds on Apple SSDs. Not sure if they even lazily flush at all. They might rely on the OS to periodically issue flushes (I heard launchd does that every 30 seconds).