High I/O delay and CPU stuck

[decibel83]

Hi.
I have an entry level server (Dell PowerEdge T30, 16 Gb RAM, 2 x 1 Tb SATA hard drives) on which I installed Proxmox 5.1 configured with a ZFS RAID1 pool.

I know this is a slow system, but after creating 3 virtual machines the server is terribly slow: continuous high I/O delay and CPU stucks on virtual machines when I make some high writes (for example restoring a mailbox or a database).

I know that upgrading to SSD should improve the performances, what about move to software RAID1?

Is there anything I can do to improve things?

I also tried to disable the ZFS sync, and this is my pveperf:

root@node1:~# pveperf
CPU BOGOMIPS:      26496.00
REGEX/SECOND:      3189958
HD SIZE:           704.91 GB (rpool/ROOT/pve-1)
FSYNCS/SECOND:     32406.06
DNS EXT:           73.75 ms
DNS INT:           8.25 ms

Thank you very much!
Bye

 

[wolfgang]

Hi,

I would say you have not enough memory.
How much memory do you apply to your VM's?

 

[decibel83]

This is the memory consumption of the virtual machine on which I have the problem:


The RAM consumption of this virtual machine is almost stable at 50% but I have ~50% peaks on I/O delay:



How I can debug the I/O delay to find out where I am out of resources?

Thanks!

 

[wolfgang]

send the output of the following command.

cat /proc/spl/kstat/zfs/arcstats
top -b -n1

 

[decibel83]

send the output of the following command.

When the virtual machine is stressed and hanged or in idle state?

Now the system is idle and I executed these commands.
You can find their output in the attached TXT file.

Thanks!

 

[wolfgang]

Your ARC cache use only 532MB this is for VM, not enough.

I would use a fix arc cache size like 6GBm but you have to test what the proper size is.

see
https://pve.proxmox.com/wiki/ZFS:_T...onfigurations_for_running_Proxmox_VE_with_ZFS