Re: Move bookworm system from SSD to NVME

The Natural Philosopher <tnp@invalid.invalid> writes:

On 02/08/2024 15:03, Björn Lundin wrote:

dd'ing 500 Gb to an ssd disk, I've seen sync taking 30 s or more
and sync is of course started AFTER dd is done
So - how do you know it is done its internal business?
Not all drives have blinking LEDs
sync makes it easy to know

 
Even sync may not be enough.
SSDS/NVM have their own internal  caching.

The sync syscall (and command) will flush those too.

Unless you’ve paid extra for a drive with a huge cache I would expect
the extra delay while the on-drive cache is flushed to be absolutely
tiny in human terms, and certainly tiny compared to flushing the OS’s
cache, which can be multiple gigabytes.

References:
* https://www.kernel.org/doc/Documentation/block/writeback_cache_control.txt
* https://linux.die.net/man/2/sync
* https://github.com/torvalds/linux/blob/master/fs/sync.c#L87

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