Stretch odd bad disk performance in VMWare ESXi

[agpastore]

Hi.

I've run into a strange issue with a brand new installation of the latest Stretch (9.1) as a virtual machine on ESXi.

I have some HP blade servers running ESXi 6.0U3 with VMDKs stored on a IBM DS4700 storage unit.
So far so good with Wheezy & Jessie.

When it comes to Strech it looks like the virtual machine is performing very badly from a disk i/o point of view.
I've noticed it on MySQL INSERT tests.

For this reason, I've done a clean install of a Jessie x64 VM and a Stretch x64 VM with no specific services other than ssh.
ESXi VM Version is 11; both have 1 vCPU and 1 GB RAM, a single 8 GB VMDK with one root partition; SCSI controller is VMWare Paravirtual,
and both machines are running their open-vm-tools.

I tried to test small consecutive write operations using dd and I've found
a huge difference between Debian v7/v8 and Debian v9.

This is the command I've used:

Code: Select all

dd if=/dev/zero of=/root/test bs=512 count=1000 oflag=dsync

This is the output on any Debian but 9 (I had similar results on v7 and v8):

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1000+0 records in
1000+0 records out
512000 bytes (512 kB) copied, 1.77293 s, 289 kB/s

This is the output on Debian Stretch:

Code: Select all

1000+0 records in
1000+0 records out
512000 bytes (512 kB, 500 KiB) copied, 9.77881 s, 52.4 kB/s

so on Stretch it takes 6x times than older releases.

Any clue on that?

Thanks,
Alberto.