Cacti: "innodb_doublewrite = off" possibly dangerous recommendation

[brenc]

Just upgraded to 1.2.4 and the installer recommended a bunch of MySQL settings, one of them being innodb_doublewrite = off if you're using SSDs. I did some checking and I'm finding is that this setting can be _dangerous_ depending on your filesystem (it can lead to data corruption). Here is some discussion on the matter. I have removed this setting from our installation.

[interduo]

Use ZFS and forget about that.

[brenc]

We don't have that option unfortunately.

[flying-bigbird]

Thanks a lot.The problem has correct!

At 2019-07-17 03:03:02, "Brendon C." [e-mail] wrote:

We don't have that option unfortunately.

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[interduo]

We don't have that option unfortunately.

So the recommendation should be conditional 'If ZFS turn off doublewrite'.

[cigamit]

I'm going to have to agree here. From research in the last few days by both @netniV and I, we can see that there are two cases at least, where this can be safely disabled, ZFS and FusionI/O cases. Otherwise, you can loose your database if someone pulls the plug or you abruptly loose power.

[brenc]

I would even go further and say that many of these settings are probably overkill for most people. I manage a fairly high qps database cluster that uses hardware RAID and SSDs and I don't even set most of these. They're not necessary except under certain circumstances and can cause other side effects. Nothing else explicitly dangerous though like this doubewrite setting.

[netniV]

Yeah hardware raid trumps double write in my opinion. This is why the SQL recommendations are just that and not enforced aside from utf8