Re:Jepsen Disputes MongoDB's Data Consistency Claims
by wolf550e on Saturday May 23, 2020 @05:15PM
(#23286529)
The default in MySQL and in postgresql is to fsync before commit and afaik that has always been the default.
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Re:Jepsen Disputes MongoDB's Data Consistency Claims
by Thaxll on Saturday May 23, 2020 @07:19PM
(#23287514)
Not it was not the case and there was several serious issues with fsync and PG in the past: https://www.percona.com/blog/2019/02/22/postgresql-fsync-fai...
On MySQL: https://dev.mysql.com/doc/refman/8.0/en/innodb-dedicated-ser...
InnoDB uses O_DIRECT during flushing I/O, but skips the fsync() system call after each write operation.
The fsync thing is more complex than it looks like.
Re:Jepsen Disputes MongoDB's Data Consistency Claims
by dijit on Saturday May 23, 2020 @07:52PM
(#23287740)
That bug was unfortunate, but you can't say that "it doesn't fsync" because, pedantically, it does, it just ignores the return value.
And, obviously that's a bug, it's designed to do so.
Also, if you write with O_DIRECT, a fsync is not needed, as it's how you tell the OS to block until written.