Linux host slow for Oracle database operations

[Maycon Oliveira]

Hi there!

Recently I bought a new server for hosting some internal programs running on VMs. Its a ThinkStation machine with Xeon processor, 128 gb RAM and 4 TB sata disk running Linux Mint 21.1. The old server was a simple machine with 32gb ram and intel i7 processor running Windows 7.

For almost all processes the performance of the new server was OK comparing with the old one, but when I start a web application server (Wildfly) pointing to the Oracle Database 12c running on a Red Hat 7 guest and when the SQL queries start to run, the performance drops a lot comparing to the old server. For comparison, a web page that used to open in 30 seconds now it took more than 2 minutes (the database is very big).

I thought that the problem was the new hardware but I tryed with another machine (i7 with 16gb ram) running Linux Mint 20 and the performance was again terrible comparing to the Windows server.

Its the same vdi on both servers.

Things that I already tryed:
- Versions 6.1 and 7 of virtualbox
- Instaling guest additions and virtualbox extensions for both version.
- Change from NAT to bridge to see if the problem was the network.
- Upgrade linux mint kernel from 5.15 to 5.19
- Changing the amount of cores available to the guest (1, 2 , 4 ou 8 )
- Increasing RAM to guest (12gb of RAM)
- Running performance test programs

What I am missing? Theres something that can i try?

Any help will be appreciated.

Thanks!

[fth0]

My primary suspect would be disk I/O (but it could also be everything else): Databases often use many small disk accesses. IOPS and latency are more important than throughput, and the domain of SSDs.

[arQon]

IO would be my first guess as well, but I'll point out that without any idea of what the DB is actually being used for the *type* of IO bottleneck can change dramatically (ie at one extreme, the bulk of the overhead could be roundtrips between userspace and kernel).

The host cache setting might be playing a part here, though I can't see that causing a 4x hit unless the guest configuration was supremely inept, which is statistically too unlikely to really consider.
Still, he does say the DB is "very big", so it would be worth checking.

[Maycon Oliveira]

Sorry for the delay.

I still dont know how windows can be faster than linux using default settings, but checking "use host i/o cache" option the performance of the linux server has increased drasticaly.

I will keep this option on for now.

Thank you for all your help!