Extremely poor write performance

Jul 27, 2017
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1
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I am using latest proxmox 4.4-13 , 3 cluster setup with freenas NAS box with NFS and SMB shares

NFS shares for VM disks (mounted on proxmox)

On 2 different servers, running 2 different OSes (win 7 and win 10) with different file formats - RAW vs qcow2 and even different controllers (SATA vs VirtIO disk)
I am getting the exact same write speed - which is Extremely poor.

I have taken some screenshots of crystaldiskmark on both VMs which I will paste below.
Mounted samba shares in windows (which is on the same ZFS pool) gives maximum performance (saturates 1gbps link), but when I run the same tests on the C drive (which is the disk specified in proxmox, I get extremely bad writes)

I am guessing there is something "obviously wrong" here but I can't figure out what.

Server 1
VM-1

OS - Windows 7 64-bit,
disk type - Raw
disk driver - VirtIO
Network - VirtIO
Cache - default

Server2
VM-2

OS - Windows 10 pro 64-bit
disk type - qcow2
disk driver - SATA
Network - VirtIO
cache - default

"C" is the local drive
"Z" is the mapped drive (network samba share on same ZFS pool)

Assumptions
- Not a cache issue as I changed the cache to "write back" but it did not make much of a difference
- Not a Disk sata/virtio driver issue as I am getting the same results from both of those configurations
- Not an OS issue as tested this with both windows 7 and windows 10
- Not a NAS or a network issue as the mapped drive (Z) gives maximum performance.
Moreover, the Read speeds look fine

This problem SEEMS to have occured after upgrading proxmox to latest version (was on an older 3.x version which I updated to latest and then did dist-upgrade)

Note - The performance was perfect when I installed proxmox for the first time (fresh install)

Screenshots below -

1) Mapped network drive on samba share on Server 1 / VM1 - Windows 7

mapped_win7_virtio_cache_def.PNG

2) Mapped network drive on samba share on Server 2 / VM2 Windows 10

mapped_win10_sata_cache_def.PNG
3) "C" drive on Server 1 / VM1 - Windows 7

win7_virtio_cache_def.PNG
4) "C" drive on Server 2 / VM2- Windows 10 (ignore the server # in screenshot)

win10_sata_cache_def.PNG
 
The difference is - default NFS configuration changes between major versions, specially between 3.x and higher.
 
You might be correct - I migrated the VMs to iSCSI storage and write performance is back! so its definitely an NFS issue.

Question is how do I fix it?
 
seems I ran across a recommended change here on the forum...
/etc/pve/storage.cfg
options vers=4, soft (instead of the vers=3)
 

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