Maybe buy battery based raid card Em sáb, 7 de set de 2019 às 15:27, Jure Sah <dustwolfy@gmail.com> escreveu:
Hi,
It would appear that on a typical webserver, the majority of disk i/o belongs to the MariaDB database process. It would appear it's mostly waiting on fsync(), which to my understanding is executed at least once per commit.
I understand that this is extensively researched in the documentation and it has to do with the recovery of data in case of an unexpected server reboot.
The thing is, this has many performance issues because it caps database performance at whatever the speed of the underlying physical storage is, even if the changed data fits into the available RAM. It also results in the circumstance where if anything is impacting performance of the storage system on the server, this will break MariaDB and cause the service to go offline (time out), even if there is sufficient RAM in the machine to continue operating as normal from page cache.
In a typical scenario you have a website which is writing things like session and page cache data which expires within an hour and would be no great loss if missing from a backup. Especially if the volume of the missing data would be 30 seconds (kernel default for committing dirty pages to disk) and mind you this setting is configurable.
Temporary tables cannot be used in this case, because they are deleted as soon as the session ends, which is too soon.
Is there a different solution that could be used here?
I've also noticed in the documentation that the options to control fsync usage are even more limited than in the MySQL server. They are also very strongly argued against. Considering the point that InnoDB is considered to be in an inconsistent state in any event, so long as the server is not cleanly stopped, is there really justification for such strong opposition here?
Disabling fsync boosts performance of a typical MySQL server by something like a factor of 3.
LP, Jure
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