Re: Public and Private network over 1 interface

[Somnath Roy <Somnath.Roy@xxxxxxxxxxx>]

4MB block size EC-object use case scenario (Mostly for reads , not so much for writes) we saw some benefit separating public/cluster network for 40GbE. We didn’t use two NIC though. We configured two ports on a NIC.

Both network can give up to 48Gb/s but with Mellanox card/Mellanox switch combination it can go up to 56Gb/s..

 

Thanks & Regards

Somnath

 

From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Brady Deetz
Sent: Monday, May 23, 2016 12:53 PM
To: ceph-users
Subject: [ceph-users] Public and Private network over 1 interface

 

TLDR;

Has anybody deployed a Ceph cluster using a single 40 gig nic? This is discouraged in http://docs.ceph.com/docs/master/rados/configuration/network-config-ref/

"One NIC OSD in a Two Network Cluster:
Generally, we do not recommend deploying an OSD host with a single NIC in a cluster with two networks. --- [cut] --- Additionally, the public network and cluster network must be able to route traffic to each other, which we don’t recommend for security reasons."

 

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Reason for this question:

My hope is that I can keep capital expenses down for this year then add a second switch and second 40 gig DAC to each node next year.

 

Thanks for any wisdom you can provide.

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Details:

Planned configuration - 40 gig interconnect via Brocade VDX 6940 and 8x OSD nodes configured as follows:

2x E5-2660v4

8x 16GB ECC DDR4 (128 GB RAM)

1x dual port Mellanox ConnectX-3 Pro EN

24x 6TB enterprise sata

2x P3700 400GB pcie nvme (journals)

2x 200GB SSD (OS drive)

 

1) From a security perspective, why not keep the networks segmented all the way to the node using tagged VLANs or VXLANs then untag them at the node? From a security perspective, that's no different than sending 2 networks to the same host on different interfaces.

 

2) By using VLANs, I wouldn't have to worry about the special configuration of Ceph mentioned in referenced documentation, since the untagged VLANs would show up as individual interfaces on the host.

 

3) From a performance perspective, has anybody observed a significant performance hit by untagging vlans on the node? This is something I can't test, since I don't currently own 40 gig gear.

 

3.a) If I used a VXLAN offloading nic, wouldn't this remove this potential issue?

 

3.a) My back of napkin estimate shows that total OSD read throughput per node could max out around 38gbps (4800MB/s). But in reality, with plenty of random I/O, I'm expecting to see something more around 30gbps. So a single 40 gig connection ought to leave plenty of headroom. right?

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