3

I have an error that annoys me enormously because it makes me crash my website at times because the IOWAIT is too high. Here is the mistake I have:

CRITICAL on CPU_IOWAIT (Min:11.3 Mean:14.1 Max:15.7): bioset, bioset, acpi_thermal_pm

when the value is too high I have an ERR_TIMEOUT that appears on my site. Is it possible to fix the problem without changing the machine? Knowing that I have a dedicated server with only 1 website above but with 5 multiboutiques (Prestashop) Thank you for your help.

Chris99391
  • 139
  • 1
  • 1
  • 4
  • 2
    Someone might find this thread over at the 'glances' github helpful; https://github.com/nicolargo/glances/issues/1214 – Dithers Feb 05 '20 at 19:52

2 Answers2

2

This means all your RAM is being used and Linux is using your disk for virtual memory, which is slow and causes iowait because it's waiting on your disk. Prestashop, PHP and MySQL can be configured in many ways that affect performance.

Kristopher Ives
  • 5,419
  • 2
  • 27
  • 36
  • the server at 32 GB ram it uses that 3 I have not seen it go above how can I solve this problem? thank you – Chris99391 Dec 25 '18 at 22:15
  • It's possible the database is very poorly optimized and it's doing a lot of table scans. You can run `iotop` or `htop` and try to see which processes are causing a heavy IO load. – Kristopher Ives Dec 26 '18 at 14:34
  • Apparently what takes the most would be [jbd2/md3-8] I do not see what know – Chris99391 Dec 26 '18 at 15:49
  • php-fpm rises at times also not bad – Chris99391 Dec 26 '18 at 15:50
  • Something is causing a large amount of disk activity, probably writing a lot to the disk. You might want to check all logs and how fast they are moving by running `find /var/log -name '*.log' | xargs tail -f` (as root) but otherwise it's likely a large amount of database activity – Kristopher Ives Dec 27 '18 at 10:56
  • these alerts are not exclusive to disk writes. They can also occur at network interfaces. See the issue on github.com/nicolargo/glances/issues/1214. There is no clear explanation so far about these alerts. – acgbox Apr 05 '23 at 00:46
0

Look for mysql change logging being disk write hotspots. Often, CMSes (Prestashop, Joomla, WP) track activities through the database, and mysql keeps log of those changes in order to be able to recover from an outage. That means a lot of writing directly to disk.

If you cannot change the CMS behavior, have a look at innodb_log_file_size (https://forums.mysql.com/read.php?22,32004,32014#msg-32014 and https://www.percona.com/blog/2006/07/03/choosing-proper-innodb_log_file_size/).

/Per

Hertzli
  • 1