Recently our MySQL server has been "going away" (ie. the client connection drops out). After weeks of trying different things (like adjusting packet size), we've discovered that it's our Veeam imaging backups which use the VMWare API to snapshot and copy the vmdks etc.
We are using ESXi 5 with a Centos 6.4 guest, running (pretty much) only MySQL 5.1.69-log.
The change which seemed to initiate this problem was increasing the physical disk size to 300GB, from about 100, and resizing the guest filesystem to use most of the new capacity. Ever since the disk was increased, we've been getting these problems during backups - presumably due to the increase time it takes to perform snapshot related functions.
The new disks are 2x300GB Gen8 15k SAS in RAID1. The old disks would have been similar only smaller. The target of the Veeam process is a ReadyNAS over a 1Gb dedicated ethernet (i.e. separated from general office traffic).
The host is an HP DL380P tower:
==server spec (BASE CHASSIS)== SERIES DL380P GEN8 PROCESSOR TYPE Intel Xeon E5-2609 v2 (2.5GHz/4-core/10MB/6.4GT-s QPI/80W) NUMBER OF PROCESSORS 2 MEMORY 80GB INTERNAL DRIVE BAYS 8 SFF HDD Bays COMPATIBLE HDD SFF SAS/SATA HARD DISK CONTROLLER SMART ARRAY P420I/ZERO MEMORY CONTROLLER (RAID 0/1/1+0)
My "IT guy" has made a few tweaks to the Veeam config including skipping empty blocks (the majority of the new disk is empty), but this didn't seem to help at all.
Veeam haven't been much help either, saying "reboot the target" or "we just use VMWare APIs".
I believe the "stun" means the virtual machine simply freezes for a time (around 30s) then continues normally.
Line 7411: 2016-06-08T17:11:44.910Z| vcpu-0| I120: Checkpoint_Unstun: vm stopped for 21068381 us Line 7556: 2016-06-08T17:22:24.608Z| vcpu-0| I120: Checkpoint_Unstun: vm stopped for 19819322 us Line 7700: 2016-06-08T17:22:30.140Z| vcpu-0| I120: Checkpoint_Unstun: vm stopped for 1130044 us Line 7929: 2016-06-08T17:23:08.616Z| vcpu-0| I120: Checkpoint_Unstun: vm stopped for 30197618 us
So my problem has two likely solutions:
Is there a way to prevent or reduce the "stunning" of a VMWare guest during imaging.
Is there a way to reduce the impact of the stun onto MySQL or the virtual network or Centos.