[PVE-User] Performance question Omnios / napp-it

Emmanuel Kasper e.kasper at proxmox.com
Mon Aug 31 10:04:53 CEST 2015

> I have set up the storage with 4x12Gbps SAS disks and a LSI 9300 HBA
> controller...
> locally on the storage i get with different random dd tests around
> 400MB/s read, which is quite okay (i dont have cache until now).
> The storage and proxmox host is direct attached with a 20Gbpe bond and i
> get around 18-19gbits with iperf..
> when I now add a ZFS over ISCSI target (with comstar) on proxmox server
> and give a test vm a virtio disk (raw) on that storage i get around
> 150-170MB/s with the same dd test...
> If I run the volume through NFS share I get around 270-300MB/s...
> Can you help me identify why iscsi is so slow? Why don't i get the same
> read/write performance inside the vm, than on the storage directly?

Hi Steffen

I don't think you can ever attain local storage performance over the
network (I am thinking about the latency of fsync calls which have to go
between the initiator and the target)

I would advise you to use something like bonnie++ to measure your I/O,
because whith dd you can't be sure if you're hitting the linux page
cache or the device itself when doing I/O

Did you have a look at https://pve.proxmox.com/wiki/Performance_Tweaks ?


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