vm7user
Enthusiast
Enthusiast

What protocol is used in VMware vSAN?

Hello,

What protocol is used in VMware vSAN?

iSCSI? FCoE? FCIP?

0 Kudos
13 Replies
pdirmann01
Enthusiast
Enthusiast

If you're referring to a host's IOPS to the physical HDD/SSDs then is all local storage so you're riding the bus from your storage controller to the disks. 

 

If you're talking about vSAN communications within the cluster, then it uses a proprietary protocol.

 

https://blogs.vmware.com/virtualblocks/2015/05/29/20-common-vsan-questions/

 

Tags (1)
0 Kudos
vm7user
Enthusiast
Enthusiast

Thanks, but where can I read a more detailed description of the protocol?

Does it run on top of ethernet frames? or on top of IP? or over another protocol?

0 Kudos
TheBobkin
VMware Employee
VMware Employee

@vm7user , RDT uses TCP protocol for data-transmission between nodes (port 2233) and UDP for cluster membership (port 12321 in modern versions). As this is a proprietary protocol you aren't going to find the specification details on external-facing pages, if you have internal-VMware access these are relatively easily found. If you are working for a 3rd-party developer that wants/needs to understand how this works then likely avenue is contacting SDK support teams to see what information they can provide.

0 Kudos
vm7user
Enthusiast
Enthusiast

I am very surprised that the slow TCP/IP network stack is used. This introduces high latencies.

test-latensy-Celsio-1024x518.jpg

0 Kudos
TheBobkin
VMware Employee
VMware Employee

@vm7user, if you think microseconds (uSec) on network transmission is the main cause of end-application (e.g at the vscsi/VM/OS-level) latency then I would advise you do more research on the entire stack that data for end-consumers of any storage solution has to traverse.

 

Will vSAN utilise/support iWARP (or any other form of RDMA) in the future? Very likely yes as this is this is an obvious path forward once enough hardware is in the field supporting these (and enough consumers using enough to not be niche).

0 Kudos
NikolayKulikov
Contributor
Contributor

10-30 uSec make no difference in real-life cases because of the end-to-end latency of All-Flash storage on the guest level is 0,5-5ms on average. Also just deviation of latency of fast enterprise NVMe SSD (not mean, but 95-99th percentile) ~ 10s-100s us. 

More than that - there were public benchmarks of vSAN on RDMA and TCP/IP a few years ago that doesn't show a huge difference - http://www.yellow-bricks.com/2018/09/05/hci2476bu-tech-preview-rdma-and-next-gen-storage-tech-for-vs...

 

 

vm7user
Enthusiast
Enthusiast

I am planning vSAN using Optane SSD with 10 us latency.

The extra latency in the network stack and software is critical.

c70db97c3e20b5a7d3078df3e32e56f4.jpg

0 Kudos
ahmet_kececiler
Contributor
Contributor

Hi,

I recommend you to  use PCI NVME for cache and normal SSD for capacity drives. In real world Full ssd vsan configs beats the full NVME optane configs. Using all Optane NVME drives does not come with the big performance difference . One of my customer have all Optane NVME 6 node they can only get 150K IOPS in 1ms aggregated latency with 16k block size. The other customer have 6 all flash ssd nodes and they get the 200k with the same tests in 1ms. The tests were done by DellEMC team . 

0 Kudos
BB9193
Contributor
Contributor

@ahmet_kececiler This is surprising.  What was the Dell/VMware response to this?  Are the configs of each deployment confirmed and verified so that no other issues could be occurring?

0 Kudos
ahmet_kececiler
Contributor
Contributor

They said  everything is normal and performance is just as expected.  I really surprised. Also ı have a deep knowledge both  VSAN and Nutanix platform i never accept the results by myself. But they said ok and the customers happy with that but i am not.

All the configs made by DellEMC and Support team checked that and everything is fine with the installations. 

And one more thing about NVMEs none of the Nutanix guys suggests using NVME drives they prefer to use ssd drives instead of NVMEs  all the times .

0 Kudos
depping
Leadership
Leadership

Just an FYI for @vm7user , starting with 7.0 Update 2, vSAN now also supports RDMA.

0 Kudos
ahmet_kececiler
Contributor
Contributor

Yes i really want to try RDMA with NVME drives.

0 Kudos