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6 Posts
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4816
February 27th, 2017 13:00
iSCSI on Shared Network
Hello,
We have a PS 6610e and 5 HP DL 380 servers running VMware 6. I've been tasked with setting up the storage to the hosts and found that we do not have any dedicated switches to use for a SAN and that we'll need to use the existing switch (Cisco Nexus 2232). I'm trying to wrap my head around how to accomplish this. I know that as a "best practice" it is better to have dedicated switches but having limited experience with this setup I'm having trouble convincing those with the $$.
From what I understand, in order to use the same network as our LAN we would need to use:
Data Center Bridging (which requires converged network adapters)?
Enable network I/O control?
I have found some information on setting this up but it is scattered - is there documentation somewhere for setting up iSCSI on a shared network? Or is this a really bad idea??
Thanks for any input/advice.
johnnva
6 Posts
0
April 11th, 2017 08:00
Don/Richard,
I apologize for a late response (had to travel for some other installs) but I really appreciate your responses. This at least gives me a starting point. I'm going to get together with our Network Admin to discuss getting what is needed on the network (or hopefully getting a separate dedicated network).
dell-richard g
605 Posts
0
March 1st, 2017 23:00
Want to add a few more details here.
Whenever a physical link is used for converged traffic, it is necessary to enable DCB on all devices (CNA-Switch-Storage). If you do not enable DCB, you are prone to packet drops on the switchport due to congestion. By enabling DCB, iSCSI traffic is considered loss-less, meaning that the switch will place higher priority on iSCSI traffic, thus not dropping such packets. Non-iSCSI traffic (such as LAN traffic) can/would be considered lossy traffic, meaning that such packets can be dropped by the switch.
Now, if your network is structure in such a way whereas each server has a different role, then it is possible to have both iSCSI and LAN traffic on the same switch. In other words, Server 1 is just for iSCSI and Server 2 is LAN traffic only. This way, each server is not running mixed traffic (converged).
But is is always important to monitor switch port statistics to determine if packet loss is occurring.
The FEX you refer to most likely does not support DCB.
If you are looking for DCB setup info, there are several sources:
1. SCSI DCB with Dell SC Series Arrays using SCOS 7.0 - Dell Community (PDF)
2. DELL Switch Configuration Guides (SCG) - details hwo to configure a switch for DCB
3. Youtube video (search on #1 above)
Also, your NIC or OS must support DCB. W2K12 and W2K16 can perfom DCB at OS level, thus your NIC does not have to have direct DCB support. The Qlogic 57810 CNA can perform DCB at the adapter level when iSCSI offload is enabled.
DCB is only configured on a switch. You do not configure it on the edge devices because the edge devices are already set to "willing mode", which means they inherit the DCB properties from the switch.
Other settings for DCB to work:
1. You must set a vlan tag (ieee 802.1q) from end-end (NIC---switch---storage)
2. LLDP must be enabled on the switch (both send and receive)
3. DCB configured and enabled on the switch
Hope this helps