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Schlagwort: 2017

Preferred settings for Macs Fan Control on older iMacs that run hot and make funny noises

Yesterday I encountered a customers iMac which ran crazy hot on the backside. Macs Fan Control indicated that the PSU was running on 70°C and more, and something made a buzzing sound (like a wire dangling inside a fan, which was not the case).

So I decided to set up the fans manually, the Mac now runs much cooler and still it's not too loud.

Here's my settings:

Set everything to manual
ODD Fan is controlled by GPU Diode. 40°C – 75°C (this controls the right hand side of the iMac)
The HDD fan is controlled by the HDD temperature. We set it to 45°C – 55°C. If your disk runs hotter, you'll shorten its lifetime and jeopardize your data. This stuff is sitting in the middle of the iMac case.
OK, and this one here is most important. Set the CPU fan to be controlled by the PSU Primary temperature.

I learned that Apple did decide to "cool" the PSU by blowing the CPUs hot air onto it. Duh. So since we need to make sure the PSU does not overheat and melt your display panels LED strips on the right side, we set the CPU fan speed in relation to the PSU temperature. We want the PSU to be 40°C – 53°C. The CPU temperature will also stay in this healthy temperature range.

Download Macs Fan Control on the dev's website, on github, or from my local mirror (v4.1.12).

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MariaDB 10.1.28 with WSREP will not start – here's how you can fix it

If you are running MariaDB 10.1 branch on any major distro (Ububtu, CentOS/RHEL…) with WSREP=ON (indicating replication such as galera), then your MariaDB systemd unit will most likely fail to start.

Steps to reproduce:

  • Install mariadb-10.1.27 or earlier for any distro
  • enable WSREP (have a cluster running)
  • upgrade one node to 10.1.28
  • mysql will simply quit any time you start the systemd unit, with no fishy warning or error messages whatsowver, just a silent insta-death.

If you now try to run mysqld (do a "which mysqld") in foreground, it will actually keep on running.

Note: use "killall mysqld" on a different shell to gracefully quit mysqld when running in foreground, because mysqld will ignore you hammering Ctrl+C, duh.

So my guess was: "This has to do with the unit file, or with mysqld_safe". Turns out i was right, after a bit of googling i found this patch for mysqld_safe, which is just broken in that release.

diff mysqld_safe.bug mysqld_safe.fixed
249c249
< local wr_logfile=$(mktemp wsrep_recovery.XXXXXX)

> local wr_logfile=$(mktemp -t wsrep_recovery.XXXXXX)
271c271
< eval_log_error "$mysqld_cmd –wsrep_recover $wr_options 2> $wr_logfile"

> eval_log_error "$mysqld_cmd –wsrep_recover $wr_options > $wr_logfile"

Source: click here

I wonder how this can happen, do they run their rpm package tests only without replication enabled!?

Of course I hit this in production, where else!? You don't run replication in testing, because nobody is willing to pay the extra server(s) 😀

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