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Mar
5
awarded  Popular Question
Aug
26
comment KVM guest network breaks under load
Disk io was also my first guess, however, the problem also occurs on less disk intensive loads.
Aug
26
asked KVM guest network breaks under load
Mar
27
revised PostgreSQL slow commit performance
added 360 characters in body
Mar
27
revised PostgreSQL slow commit performance
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Mar
27
comment PostgreSQL slow commit performance
I have amended my original question with additional information about mount options and partition alignment.
Mar
27
revised PostgreSQL slow commit performance
added 1624 characters in body
Mar
27
comment PostgreSQL slow commit performance
I ran bonnie++ which shows good performance (as good as you'd expect from regular sata disks). Also, the partitions are aligned. When I ran pg_test_fsync the first time it was on a VM. Then I ran it on the actual hardware, after shutting down every other process (including VMs). The performance was slightly better, around 40 ops/sec, which is still deplorable. I'm going to run some more tests, on separate partitions if I got the time today. Thanks for all the suggestions.
Mar
25
comment PostgreSQL slow commit performance
Just checked, the firmware on both disks is at the latest version (CC4H).
Mar
25
comment PostgreSQL slow commit performance
I have amended my original question with information about the disk types. In the meantime I tried setting noatime and killed all other processes (when possible) on the machine. This increases the performance two-fold, from extremely bad, to just really bad.
Mar
25
revised PostgreSQL slow commit performance
added 150 characters in body
Mar
25
awarded  Commentator
Mar
25
comment PostgreSQL slow commit performance
The short smart test on both disks revealed no problems, I started long tests on both, and will check the results asap. dmesg and the syslog showed no errors. I checked the partition aligned friday, they are aligned on 4k boundaries, also, the disks use GPT, so fdisk -l doesn't show useful output.
Mar
22
revised PostgreSQL slow commit performance
added 44 characters in body
Mar
22
comment PostgreSQL slow commit performance
I have updated the question with more details about the filesystem and raid config. I understand that this machine is never going to give very good performance in it's current configuration. But the current performance is really bad.
Mar
22
revised PostgreSQL slow commit performance
Formatting
Mar
22
comment PostgreSQL slow commit performance
I tried running pg_test_fsync on my own SSD, and I get comparable performance figures. I know that I could disable sync commits, but the question remains, what is the cause of this problem?
Mar
22
comment PostgreSQL slow commit performance
Yes, but what is causing the bad fsync performance?
Mar
22
revised PostgreSQL slow commit performance
added 75 characters in body
Mar
22
asked PostgreSQL slow commit performance