I have 2 SSDs set up in RAID 0 configuration with a single volume on them that I've been using without problems for 3 months straight to run a PostgreSQL database. Suddenly, today, the DB got really slow. I used to run multiple queries on huge tables and see 100% CPU usage for each postgres
task (I have 12 cores). Now, one query by itself uses 15%-30% CPU, as if there's a disk bottleneck, and the same queries with the same data are taking much longer to run.
I don't know if this was happening before, but if I run iotop
, I see kworker/u24:1
using 99.99% IO and 0 disk read and write. I don't know if that's normal, but it looks suspicious.
I ran benchmarks with dd
and hdparm
. The SSD read/write time looks fast enough; no problem there. RAM usage is fine. I see almost no swap used. I have very little free because all the free memory goes to disk caching, but that's supposed to be OK. I don't actually have any processes using up all my RAM.
What's the deal with kworker
? I know it's a kernel task. Is it a problem that it's using so many IOs? Anything I should check?
Update: It stopped doing it. Not sure when or why.
Update Time : Sun Dec 20 16:54:20 2015
(which is when I built the array).