iSCSI and networking

[JBK]

I have been looking through the forums for different information on iSCSI and best practices and I have found some very good results. I do have a couple of questions for anyone using iSCSI out there who happens to be an expert.. or experienced. Is there any benefit to going with 20 gig LAG as opposed to just using a single 10 gig interface? Also, are jumbo frames really that big of an advantage? All I am doing is file level in and out all - 2 MB non-compressible files. This is just an ordinary file server. Any input would be appreciated and thank you in advance.

I have already done my low level testing with drives and settings and vdevs, now I am ready to go to production testing but I want to get it right the first time and not waste resources if they are not necessary.

Front-end is Windows server 2019 (as a SMB server) and the iSCSI back-end will be on a private 10gig switch isolated from the general network.

 

[Samuel Tai]

LAGGs for iSCSI aren't worth the trouble, as you only end up using one of the LAGG members in practice. Better would be to set up multipath over both 10G interfaces, as both paths will be in use. Make sure to configure the multipath members on different subnets. The iSCSI clients would also need to have interfaces on both subnets to take advantage of multipath.

 

[JBK]

Good information, thank you. Yes I like multipath, I just wish I did not have to use isolated VLANs - I know there is a long discussion/argument on the community about that but Netapp does it better.

So what about Jumbo frames? I know there are advantages on file traffic but how does it affect block? Is it worth it? It is just one more thing you have to deal with.

 

[Samuel Tai]

Without knowing the specifics of your environment, I can't say if jumbo frames would hurt or help. All the devices in the isolated VLAN(s) would need to support jumbo frames to enable success with jumbo frames. Otherwise, you'll see worse performance if one or 2 devices don't, and tracking them down can be very frustrating.

 

[JBK]

Nice. Thank you. Just two windows servers with an iSCSI backend. Simple file server, no SQL or applications. Nexus 5K as iSCSI switch and I can qos the ports to use jumbo if necessary. I will test, that is easy enough to change. Thank you again.